March 2009 - logback-dev - mailman3.qos.ch

[JIRA] Created: (LBCLASSIC-111) Improve performance by removing StringBuffer where possible
by Rick Beton (JIRA) 15 Mar '09

15 Mar '09

Improve performance by removing StringBuffer where possible ----------------------------------------------------------- Key: LBCLASSIC-111 URL: http://jira.qos.ch/browse/LBCLASSIC-111 Project: logback-classic Issue Type: Bug Affects Versions: 0.9.15 Environment: any Reporter: Rick Beton Assignee: Logback dev list Priority: Minor StringBuffer is used in some local variables. The newer StringBuilder alternative will improve the performance slightly in such cases. E.g.in FileNamePattern public String convert(Object o) { Converter<Object> p = headTokenConverter; StringBuffer buf = new StringBuffer(); while (p != null) { buf.append(p.convert(o)); p = p.getNext(); } return buf.toString(); } should change to use StringBuilder buf = new StringBuilder(); -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://jira.qos.ch/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira

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[JIRA] Created: (LBACCESS-9) Please make the LoggerContext of an AccessEvent accessible
by Joern Huxhorn (JIRA) 13 Mar '09

13 Mar '09

Please make the LoggerContext of an AccessEvent accessible ---------------------------------------------------------- Key: LBACCESS-9 URL: http://jira.qos.ch/browse/LBACCESS-9 Project: logback-access Issue Type: New Feature Reporter: Joern Huxhorn Assignee: Logback dev list See http://qos.ch/pipermail/logback-dev/2009-March/003867.html I'd like to use the LoggerContext properties for filtering purposes. At the moment, both my Lilith multiplex-appenders contain support for an ApplicationIdentifier. In case of LoggingEvent, I changed the behavior of this property. It is now, if set, put into the properties of the LoggerContext. This isn't possible in case of AccessEvent because I can't access it's context, yet. The primary use of this property is ease of use while filtering events. While it would certainly be possible to deduce information about the logging application, it's easier and less error prone to simply use a manual identifier. My application identifier was a bit short-sighted so I'd like to just use any logger context properties for filtering. Thanks in advance, Joern. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://jira.qos.ch/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira

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Question about LoggerContext.putProperty and putObject
by Joern Huxhorn 13 Mar '09

13 Mar '09

Hi, I'd like to know if it's possible to set properties and/or objects of the LoggerContext using a standard joran config file. At the moment, my own appender has a setApplicationIdentifier so I'm able to easily identify different apps running on the same host. Would it be possible to use the mentioned LoggerContext methods for this? Joern.

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svn commit: r2209 - logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus
by noreply.ceki＠qos.ch 11 Mar '09

11 Mar '09

Author: ceki Date: Wed Mar 11 21:56:16 2009 New Revision: 2209 Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java Log: changed the level distribution Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java Wed Mar 11 21:56:16 2009 @@ -52,9 +52,9 @@ static final int LOG_STATEMENT_POOL_SIZE = LOGGER_POOL_SIZE * 8; // level distribution is determined by the following table - // It corresponds to TRACE 20%, DEBUG 30%, INFO 30%, WARN 10%, - // ERROR 10%. See also getRandomLevel() method. - static final double[] LEVEL_DISTRIBUTION = new double[] { .2, .5, .8, .9 }; + // It corresponds to TRACE 3%, DEBUG 30%, INFO 30%, WARN 5%, + // ERROR 5%. See also getRandomLevel() method. + static final double[] LEVEL_DISTRIBUTION = new double[] { .3, .3, .9, .95 }; // It is assumed that the number of words in the message (contained in a log // statement) is a random variable normally distributed with mean @@ -187,7 +187,7 @@ public CallerData[] getRandomCallerData(int depth, String loggerName) { CallerData[] cda = new CallerData[depth]; CallerData cd = new CallerData(extractLastPart(loggerName), loggerName, - getRandomJavaIdentifier(), 10); + getRandomJavaIdentifier(), 0); cda[0] = cd; for (int i = 1; i < depth; i++) { String ln = getRandomLoggerNameFromPool(loggerNamePool);

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svn commit: r2205 - logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus
by noreply.ceki＠qos.ch 10 Mar '09

10 Mar '09

Author: ceki Date: Tue Mar 10 16:25:26 2009 New Revision: 2205 Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java Log: had erroneously forgot to set throwable proxy Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java Tue Mar 10 16:25:26 2009 @@ -83,6 +83,7 @@ e.callerDataArray = corpusModel.getRandomCallerData( ClassicConstants.DEFAULT_MAX_CALLEDER_DATA_DEPTH, e.loggerName); } + e.throwableProxy = logStatement.throwableProxy; e.threadName = corpusModel.getRandomThreadNameFromPool(); } return plevoArray;

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svn commit: r2202 - logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus
by noreply.ceki＠qos.ch 10 Mar '09

10 Mar '09

Author: ceki Date: Tue Mar 10 15:14:22 2009 New Revision: 2202 Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java Log: - CorpusModel will optionally include caller data. - The standard corpus now includes caller data. Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/Corpus.java Tue Mar 10 15:14:22 2009 @@ -14,6 +14,7 @@ import java.net.URL; import java.util.List; +import ch.qos.logback.classic.ClassicConstants; import ch.qos.logback.classic.spi.ILoggingEvent; import ch.qos.logback.classic.spi.IThrowableProxy; import ch.qos.logback.classic.spi.LoggerContextVO; @@ -58,10 +59,11 @@ static public ILoggingEvent[] makeStandardCorpus() throws IOException { List<String> worldList = getStandatdCorpusWordList(); CorpusModel corpusMaker = new CorpusModel(STANDARD_SEED, worldList); - return make(corpusMaker, STANDARD_CORPUS_SIZE); + return make(corpusMaker, STANDARD_CORPUS_SIZE, true); } - static public ILoggingEvent[] make(CorpusModel corpusModel, int n) { + static public ILoggingEvent[] make(CorpusModel corpusModel, int n, + boolean withCallerData) { LoggerContextVO lcVO = corpusModel.getRandomlyNamedLoggerContextVO(); PubLoggingEventVO[] plevoArray = new PubLoggingEventVO[n]; for (int i = 0; i < n; i++) { @@ -76,7 +78,11 @@ e.message = logStatement.mat.message; e.argumentArray = corpusModel .getRandomArgumentArray(logStatement.mat.numberOfArguments); - e.throwableProxy = logStatement.throwableProxy; + + if (withCallerData) { + e.callerDataArray = corpusModel.getRandomCallerData( + ClassicConstants.DEFAULT_MAX_CALLEDER_DATA_DEPTH, e.loggerName); + } e.threadName = corpusModel.getRandomThreadNameFromPool(); } return plevoArray; Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusModel.java Tue Mar 10 15:14:22 2009 @@ -14,6 +14,7 @@ import ch.qos.logback.classic.Level; import ch.qos.logback.classic.LoggerContext; +import ch.qos.logback.classic.spi.CallerData; import ch.qos.logback.classic.spi.ClassPackagingData; import ch.qos.logback.classic.spi.LoggerContextVO; import ch.qos.logback.classic.spi.StackTraceElementProxy; @@ -84,6 +85,7 @@ final List<String> worldList; String[] threadNamePool; LogStatement[] logStatementPool; + String[] loggerNamePool; // 2009-03-06 13:08 GMT long lastTimeStamp = 1236344888578L; @@ -92,6 +94,7 @@ random = new Random(seed); this.worldList = worldList; buildThreadNamePool(); + buildLoggerNamePool(); buildLogStatementPool(); } @@ -102,11 +105,14 @@ } } - private void buildLogStatementPool() { - String[] loggerNamePool = new String[LOGGER_POOL_SIZE]; + private void buildLoggerNamePool() { + loggerNamePool = new String[LOGGER_POOL_SIZE]; for (int i = 0; i < LOGGER_POOL_SIZE; i++) { loggerNamePool[i] = makeRandomLoggerName(); } + } + + private void buildLogStatementPool() { logStatementPool = new LogStatement[LOG_STATEMENT_POOL_SIZE]; for (int i = 0; i < LOG_STATEMENT_POOL_SIZE; i++) { logStatementPool[i] = makeRandomLogStatement(loggerNamePool); @@ -169,6 +175,28 @@ return worldList.get(randomIndex); } + String extractLastPart(String loggerName) { + int i = loggerName.lastIndexOf('.'); + if (i == -1) { + return loggerName; + } else { + return loggerName.substring(i + 1); + } + } + + public CallerData[] getRandomCallerData(int depth, String loggerName) { + CallerData[] cda = new CallerData[depth]; + CallerData cd = new CallerData(extractLastPart(loggerName), loggerName, + getRandomJavaIdentifier(), 10); + cda[0] = cd; + for (int i = 1; i < depth; i++) { + String ln = getRandomLoggerNameFromPool(loggerNamePool); + cda[i] = new CallerData(extractLastPart(ln), ln, + getRandomJavaIdentifier(), i * 10); + } + return cda; + } + public Object[] getRandomArgumentArray(int numOfArguments) { if (numOfArguments == 0) { return null;

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[JIRA] Resolved: (LBCORE-45) introduce FlushableAppender
by Ceki Gulcu (JIRA) 09 Mar '09

09 Mar '09

[ http://jira.qos.ch/browse/LBCORE-45?page=com.atlassian.jira.plugin.system.i… ] Ceki Gulcu resolved LBCORE-45. ------------------------------ Resolution: Duplicate > introduce FlushableAppender > --------------------------- > > Key: LBCORE-45 > URL: http://jira.qos.ch/browse/LBCORE-45 > Project: logback-core > Issue Type: Improvement > Components: Appender > Affects Versions: unspecified > Environment: Operating System: Linux > Platform: PC > Reporter: Bruno Navert > Assignee: Ceki Gulcu > Priority: Minor > > Suggest a new sub-interface of Appender: > public interface FlushableAppender<E> extends Appender<E>, java.io.Flushable > { > } > Then, WriterAppender could be defined to implement FlushableAppender, with this simple implementation: > public void flush() throws IOException > { > writer.flush(); > } > This would allow manual flushing of the appenders. This is particularly useful when buffered IO is used, obviously. It allows, for instance, to manually flush all appenders when a request has been fully processed, ensuring that we retain the benefits of buffered IO while also having the full logs after request processing. > Here's sample code I used to get all appenders (run once after Logback configuration): > public static Set<Appender> getAllAppenders() > { > ContextSelector selector = StaticLoggerBinder.SINGLETON.getContextSelector(); > LoggerContext loggerContext = selector.getLoggerContext(); > Map<String, Appender> appenders = newHashMap(); > // loop through all Loggers > for ( Logger logger : loggerContext.getLoggerList() ) > { > // for each logger, loop through all its appenders > Iterator iter = logger.iteratorForAppenders(); > while ( iter.hasNext() ) > { > // appenders are uniquely identified by name, so store them in the Map thus > // this will overwrite the same entry in the Map many times (with the same reference) > Appender appender = ( Appender ) iter.next(); > appenders.put( appender.getName(), appender ); > } > } > return newHashSet( appenders.values() ); > } > The below bean is used in Spring, calling flush() forces all appenders to be flushed: > public class LogbackFlushBean implements Flushable > { > protected final Logger log = LoggerFactory.getLogger( getClass() ); > private final Collection<FlushableAppender> flushableAppenders = newLinkedList(); > @PostConstruct > public void loadFlushableAppenders() > { > for ( Appender appender : LogbackConfigurer.getAllAppenders() ) > { > if ( appender instanceof FlushableAppender ) > { > flushableAppenders.add( ( FlushableAppender ) appender ); > } > else > { > log.debug( "appender {} is not Flushable, skipping", appender.getName() ); > } > } > } > public void flush() throws IOException > { > for ( FlushableAppender appender : flushableAppenders ) > { > log.debug( "flushing appender {}", appender.getName() ); > appender.flush(); > } > } > } -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://jira.qos.ch/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira

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[JIRA] Commented: (LBCORE-45) introduce FlushableAppender
by Ceki Gulcu (JIRA) 09 Mar '09

09 Mar '09

[ http://jira.qos.ch/browse/LBCORE-45?page=com.atlassian.jira.plugin.system.i… ] Ceki Gulcu commented on LBCORE-45: ---------------------------------- There are two details to consider. 1) when streams are closed they are also flushed 2) only a single thread can access a stream at a time Passing the underlying output stream to the flushing policy would break encapsulation, which can't be allows. Instead, here is how I current envision FlushingPolicy: interface FlushingPolicy { booelan shouldFlush(LoggingEvent e); } Thus, flushing policy could be based on any criteria available to the shouldFlush() method, including time. As for the FLUSH marker, it is just one possible approach for "manually flushing appenders when a request has been fully processed" which you asked for. > introduce FlushableAppender > --------------------------- > > Key: LBCORE-45 > URL: http://jira.qos.ch/browse/LBCORE-45 > Project: logback-core > Issue Type: Improvement > Components: Appender > Affects Versions: unspecified > Environment: Operating System: Linux > Platform: PC > Reporter: Bruno Navert > Assignee: Ceki Gulcu > Priority: Minor > > Suggest a new sub-interface of Appender: > public interface FlushableAppender<E> extends Appender<E>, java.io.Flushable > { > } > Then, WriterAppender could be defined to implement FlushableAppender, with this simple implementation: > public void flush() throws IOException > { > writer.flush(); > } > This would allow manual flushing of the appenders. This is particularly useful when buffered IO is used, obviously. It allows, for instance, to manually flush all appenders when a request has been fully processed, ensuring that we retain the benefits of buffered IO while also having the full logs after request processing. > Here's sample code I used to get all appenders (run once after Logback configuration): > public static Set<Appender> getAllAppenders() > { > ContextSelector selector = StaticLoggerBinder.SINGLETON.getContextSelector(); > LoggerContext loggerContext = selector.getLoggerContext(); > Map<String, Appender> appenders = newHashMap(); > // loop through all Loggers > for ( Logger logger : loggerContext.getLoggerList() ) > { > // for each logger, loop through all its appenders > Iterator iter = logger.iteratorForAppenders(); > while ( iter.hasNext() ) > { > // appenders are uniquely identified by name, so store them in the Map thus > // this will overwrite the same entry in the Map many times (with the same reference) > Appender appender = ( Appender ) iter.next(); > appenders.put( appender.getName(), appender ); > } > } > return newHashSet( appenders.values() ); > } > The below bean is used in Spring, calling flush() forces all appenders to be flushed: > public class LogbackFlushBean implements Flushable > { > protected final Logger log = LoggerFactory.getLogger( getClass() ); > private final Collection<FlushableAppender> flushableAppenders = newLinkedList(); > @PostConstruct > public void loadFlushableAppenders() > { > for ( Appender appender : LogbackConfigurer.getAllAppenders() ) > { > if ( appender instanceof FlushableAppender ) > { > flushableAppenders.add( ( FlushableAppender ) appender ); > } > else > { > log.debug( "appender {} is not Flushable, skipping", appender.getName() ); > } > } > } > public void flush() throws IOException > { > for ( FlushableAppender appender : flushableAppenders ) > { > log.debug( "flushing appender {}", appender.getName() ); > appender.flush(); > } > } > } -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://jira.qos.ch/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira

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svn commit: r2179 - in logback/trunk/logback-classic/src/test: input/corpus java/ch/qos/logback/classic/control java/ch/qos/logback/classic/corpus java/ch/qos/logback/classic/corpusTest
by noreply.ceki＠qos.ch 09 Mar '09

09 Mar '09

Author: ceki Date: Wed Mar 4 21:05:53 2009 New Revision: 2179 Added: logback/trunk/logback-classic/src/test/input/corpus/ logback/trunk/logback-classic/src/test/input/corpus/origin_of_species.txt logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusMakerUtil.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/MessageEntry.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/RandomUtil.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/TextFileUtil.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/FileToWord.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/RandomUtilTest.java Removed: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/RandomUtilTest.java Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/PackageTest.java logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/ScenarioRandomUtil.java Log: Started work on the corpus. Added: logback/trunk/logback-classic/src/test/input/corpus/origin_of_species.txt ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/input/corpus/origin_of_species.txt Wed Mar 4 21:05:53 2009 @@ -0,0 +1,1276 @@ +Darwin, Charles, 1809-1882 + +ON THE ORIGIN OF SPECIES. + +INTRODUCTION. + +When on board H.M.S. 'Beagle,' as naturalist, I was much struck with +certain facts in the distribution of the inhabitants of South America, +and in the geological relations of the present to the past inhabitants +of that continent. These facts seemed to me to throw some light on the +origin of species--that mystery of mysteries, as it has been called by +one of our greatest philosophers. On my return home, it occurred to +me, in 1837, that something might perhaps be made out on this question +by patiently accumulating and reflecting on all sorts of facts which +could possibly have any bearing on it. After five years' work I +allowed myself to speculate on the subject, and drew up some short +notes; these I enlarged in 1844 into a sketch of the conclusions, +which then seemed to me probable: from that period to the present day +I have steadily pursued the same object. I hope that I may be excused +for entering on these personal details, as I give them to show that I +have not been hasty in coming to a decision. + +My work is now nearly finished; but as it will take me two or three +more years to complete it, and as my health is far from strong, I have +been urged to publish this Abstract. I have more especially been +induced to do this, as Mr. Wallace, who is now studying the natural +history of the Malay archipelago, has arrived at almost exactly the +same general conclusions that I have on the origin of species. Last +year he sent to me a memoir on this subject, with a request that I +would forward it to Sir Charles Lyell, who sent it to the Linnean +Society, and it is published in the third volume of the Journal of +that Society. Sir C. Lyell and Dr. Hooker, who both knew of my +work--the latter having read my sketch of 1844--honoured me by +thinking it advisable to publish, with Mr. Wallace's excellent memoir, +some brief extracts from my manuscripts. + +This Abstract, which I now publish, must necessarily be imperfect. I +cannot here give references and authorities for my several statements; +and I must trust to the reader reposing some confidence in my +accuracy. No doubt errors will have crept in, though I hope I have +always been cautious in trusting to good authorities alone. I can here +give only the general conclusions at which I have arrived, with a few +facts in illustration, but which, I hope, in most cases will suffice. +No one can feel more sensible than I do of the necessity of hereafter +publishing in detail all the facts, with references, on which my +conclusions have been grounded; and I hope in a future work to do +this. For I am well aware that scarcely a single point is discussed in +this volume on which facts cannot be adduced, often apparently leading +to conclusions directly opposite to those at which I have arrived. A +fair result can be obtained only by fully stating and balancing the +facts and arguments on both sides of each question; and this cannot +possibly be here done. + +I much regret that want of space prevents my having the satisfaction +of acknowledging the generous assistance which I have received from +very many naturalists, some of them personally unknown to me. I +cannot, however, let this opportunity pass without expressing my deep +obligations to Dr. Hooker, who for the last fifteen years has aided me +in every possible way by his large stores of knowledge and his +excellent judgment. + +In considering the Origin of Species, it is quite conceivable that a +naturalist, reflecting on the mutual affinities of organic beings, on +their embryological relations, their geographical distribution, +geological succession, and other such facts, might come to the +conclusion that each species had not been independently created, but +had descended, like varieties, from other species. Nevertheless, such +a conclusion, even if well founded, would be unsatisfactory, until it +could be shown how the innumerable species inhabiting this world have +been modified, so as to acquire that perfection of structure and +coadaptation which most justly excites our admiration. Naturalists +continually refer to external conditions, such as climate, food, etc., +as the only possible cause of variation. In one very limited sense, as +we shall hereafter see, this may be true; but it is preposterous to +attribute to mere external conditions, the structure, for instance, of +the woodpecker, with its feet, tail, beak, and tongue, so admirably +adapted to catch insects under the bark of trees. In the case of the +misseltoe, which draws its nourishment from certain trees, which has +seeds that must be transported by certain birds, and which has flowers +with separate sexes absolutely requiring the agency of certain insects +to bring pollen from one flower to the other, it is equally +preposterous to account for the structure of this parasite, with its +relations to several distinct organic beings, by the effects of +external conditions, or of habit, or of the volition of the plant +itself. + +The author of the 'Vestiges of Creation' would, I presume, say that, +after a certain unknown number of generations, some bird had given +birth to a woodpecker, and some plant to the misseltoe, and that these +had been produced perfect as we now see them; but this assumption +seems to me to be no explanation, for it leaves the case of the +coadaptations of organic beings to each other and to their physical +conditions of life, untouched and unexplained. + +It is, therefore, of the highest importance to gain a clear insight +into the means of modification and coadaptation. At the commencement +of my observations it seemed to me probable that a careful study of +domesticated animals and of cultivated plants would offer the best +chance of making out this obscure problem. Nor have I been +disappointed; in this and in all other perplexing cases I have +invariably found that our knowledge, imperfect though it be, of +variation under domestication, afforded the best and safest clue. I +may venture to express my conviction of the high value of such +studies, although they have been very commonly neglected by +naturalists. + +From these considerations, I shall devote the first chapter of this +Abstract to Variation under Domestication. We shall thus see that a +large amount of hereditary modification is at least possible, and, +what is equally or more important, we shall see how great is the power +of man in accumulating by his Selection successive slight variations. +I will then pass on to the variability of species in a state of +nature; but I shall, unfortunately, be compelled to treat this subject +far too briefly, as it can be treated properly only by giving long +catalogues of facts. We shall, however, be enabled to discuss what +circumstances are most favourable to variation. In the next chapter +the Struggle for Existence amongst all organic beings throughout the +world, which inevitably follows from their high geometrical powers of +increase, will be treated of. This is the doctrine of Malthus, applied +to the whole animal and vegetable kingdoms. As many more individuals +of each species are born than can possibly survive; and as, +consequently, there is a frequently recurring struggle for existence, +it follows that any being, if it vary however slightly in any manner +profitable to itself, under the complex and sometimes varying +conditions of life, will have a better chance of surviving, and thus +be NATURALLY SELECTED. From the strong principle of inheritance, any +selected variety will tend to propagate its new and modified form. + +This fundamental subject of Natural Selection will be treated at some +length in the fourth chapter; and we shall then see how Natural +Selection almost inevitably causes much Extinction of the less +improved forms of life and induces what I have called Divergence of +Character. In the next chapter I shall discuss the complex and little +known laws of variation and of correlation of growth. In the four +succeeding chapters, the most apparent and gravest difficulties on the +theory will be given: namely, first, the difficulties of transitions, +or in understanding how a simple being or a simple organ can be +changed and perfected into a highly developed being or elaborately +constructed organ; secondly the subject of Instinct, or the mental +powers of animals, thirdly, Hybridism, or the infertility of species +and the fertility of varieties when intercrossed; and fourthly, the +imperfection of the Geological Record. In the next chapter I shall +consider the geological succession of organic beings throughout time; +in the eleventh and twelfth, their geographical distribution +throughout space; in the thirteenth, their classification or mutual +affinities, both when mature and in an embryonic condition. In the +last chapter I shall give a brief recapitulation of the whole work, +and a few concluding remarks. + +No one ought to feel surprise at much remaining as yet unexplained in +regard to the origin of species and varieties, if he makes due +allowance for our profound ignorance in regard to the mutual relations +of all the beings which live around us. Who can explain why one +species ranges widely and is very numerous, and why another allied +species has a narrow range and is rare? Yet these relations are of the +highest importance, for they determine the present welfare, and, as I +believe, the future success and modification of every inhabitant of +this world. Still less do we know of the mutual relations of the +innumerable inhabitants of the world during the many past geological +epochs in its history. Although much remains obscure, and will long +remain obscure, I can entertain no doubt, after the most deliberate +study and dispassionate judgment of which I am capable, that the view +which most naturalists entertain, and which I formerly +entertained--namely, that each species has been independently +created--is erroneous. I am fully convinced that species are not +immutable; but that those belonging to what are called the same genera +are lineal descendants of some other and generally extinct species, in +the same manner as the acknowledged varieties of any one species are +the descendants of that species. Furthermore, I am convinced that +Natural Selection has been the main but not exclusive means of +modification. + +CHAPTER 1. VARIATION UNDER DOMESTICATION. + +Causes of Variability. +Effects of Habit. +Correlation of Growth. +Inheritance. +Character of Domestic Varieties. +Difficulty of distinguishing between Varieties and Species. +Origin of Domestic Varieties from one or more Species. +Domestic Pigeons, their Differences and Origin. +Principle of Selection anciently followed, its Effects. +Methodical and Unconscious Selection. +Unknown Origin of our Domestic Productions. +Circumstances favourable to Man's power of Selection. + +When we look to the individuals of the same variety or sub-variety of +our older cultivated plants and animals, one of the first points which +strikes us, is, that they generally differ much more from each other, +than do the individuals of any one species or variety in a state of +nature. When we reflect on the vast diversity of the plants and +animals which have been cultivated, and which have varied during all +ages under the most different climates and treatment, I think we are +driven to conclude that this greater variability is simply due to our +domestic productions having been raised under conditions of life not +so uniform as, and somewhat different from, those to which the +parent-species have been exposed under nature. There is, also, I +think, some probability in the view propounded by Andrew Knight, that +this variability may be partly connected with excess of food. It seems +pretty clear that organic beings must be exposed during several +generations to the new conditions of life to cause any appreciable +amount of variation; and that when the organisation has once begun to +vary, it generally continues to vary for many generations. No case is +on record of a variable being ceasing to be variable under +cultivation. Our oldest cultivated plants, such as wheat, still often +yield new varieties: our oldest domesticated animals are still capable +of rapid improvement or modification. + +It has been disputed at what period of life the causes of variability, +whatever they may be, generally act; whether during the early or late +period of development of the embryo, or at the instant of conception. +Geoffroy St. Hilaire's experiments show that unnatural treatment of +the embryo causes monstrosities; and monstrosities cannot be separated +by any clear line of distinction from mere variations. But I am +strongly inclined to suspect that the most frequent cause of +variability may be attributed to the male and female reproductive +elements having been affected prior to the act of conception. Several +reasons make me believe in this; but the chief one is the remarkable +effect which confinement or cultivation has on the functions of the +reproductive system; this system appearing to be far more susceptible +than any other part of the organisation, to the action of any change +in the conditions of life. Nothing is more easy than to tame an +animal, and few things more difficult than to get it to breed freely +under confinement, even in the many cases when the male and female +unite. How many animals there are which will not breed, though living +long under not very close confinement in their native country! This is +generally attributed to vitiated instincts; but how many cultivated +plants display the utmost vigour, and yet rarely or never seed! In +some few such cases it has been found out that very trifling changes, +such as a little more or less water at some particular period of +growth, will determine whether or not the plant sets a seed. I cannot +here enter on the copious details which I have collected on this +curious subject; but to show how singular the laws are which determine +the reproduction of animals under confinement, I may just mention that +carnivorous animals, even from the tropics, breed in this country +pretty freely under confinement, with the exception of the +plantigrades or bear family; whereas, carnivorous birds, with the +rarest exceptions, hardly ever lay fertile eggs. Many exotic plants +have pollen utterly worthless, in the same exact condition as in the +most sterile hybrids. When, on the one hand, we see domesticated +animals and plants, though often weak and sickly, yet breeding quite +freely under confinement; and when, on the other hand, we see +individuals, though taken young from a state of nature, perfectly +tamed, long-lived, and healthy (of which I could give numerous +instances), yet having their reproductive system so seriously affected +by unperceived causes as to fail in acting, we need not be surprised +at this system, when it does act under confinement, acting not quite +regularly, and producing offspring not perfectly like their parents or +variable. + +Sterility has been said to be the bane of horticulture; but on this +view we owe variability to the same cause which produces sterility; +and variability is the source of all the choicest productions of the +garden. I may add, that as some organisms will breed most freely under +the most unnatural conditions (for instance, the rabbit and ferret +kept in hutches), showing that their reproductive system has not been +thus affected; so will some animals and plants withstand domestication +or cultivation, and vary very slightly--perhaps hardly more than in a +state of nature. + +A long list could easily be given of "sporting plants;" by this term +gardeners mean a single bud or offset, which suddenly assumes a new +and sometimes very different character from that of the rest of the +plant. Such buds can be propagated by grafting, etc., and sometimes by +seed. These "sports" are extremely rare under nature, but far from +rare under cultivation; and in this case we see that the treatment of +the parent has affected a bud or offset, and not the ovules or pollen. +But it is the opinion of most physiologists that there is no essential +difference between a bud and an ovule in their earliest stages of +formation; so that, in fact, "sports" support my view, that +variability may be largely attributed to the ovules or pollen, or to +both, having been affected by the treatment of the parent prior to the +act of conception. These cases anyhow show that variation is not +necessarily connected, as some authors have supposed, with the act of +generation. + +Seedlings from the same fruit, and the young of the same litter, +sometimes differ considerably from each other, though both the young +and the parents, as Muller has remarked, have apparently been exposed +to exactly the same conditions of life; and this shows how unimportant +the direct effects of the conditions of life are in comparison with +the laws of reproduction, and of growth, and of inheritance; for had +the action of the conditions been direct, if any of the young had +varied, all would probably have varied in the same manner. To judge +how much, in the case of any variation, we should attribute to the +direct action of heat, moisture, light, food, etc., is most difficult: +my impression is, that with animals such agencies have produced very +little direct effect, though apparently more in the case of plants. +Under this point of view, Mr. Buckman's recent experiments on plants +seem extremely valuable. When all or nearly all the individuals +exposed to certain conditions are affected in the same way, the change +at first appears to be directly due to such conditions; but in some +cases it can be shown that quite opposite conditions produce similar +changes of structure. Nevertheless some slight amount of change may, I +think, be attributed to the direct action of the conditions of +life--as, in some cases, increased size from amount of food, colour +from particular kinds of food and from light, and perhaps the +thickness of fur from climate. + +Habit also has a decided influence, as in the period of flowering with +plants when transported from one climate to another. In animals it has +a more marked effect; for instance, I find in the domestic duck that +the bones of the wing weigh less and the bones of the leg more, in +proportion to the whole skeleton, than do the same bones in the +wild-duck; and I presume that this change may be safely attributed to +the domestic duck flying much less, and walking more, than its wild +parent. The great and inherited development of the udders in cows and +goats in countries where they are habitually milked, in comparison +with the state of these organs in other countries, is another instance +of the effect of use. Not a single domestic animal can be named which +has not in some country drooping ears; and the view suggested by some +authors, that the drooping is due to the disuse of the muscles of the +ear, from the animals not being much alarmed by danger, seems +probable. + +There are many laws regulating variation, some few of which can be +dimly seen, and will be hereafter briefly mentioned. I will here only +allude to what may be called correlation of growth. Any change in the +embryo or larva will almost certainly entail changes in the mature +animal. In monstrosities, the correlations between quite distinct +parts are very curious; and many instances are given in Isidore +Geoffroy St. Hilaire's great work on this subject. Breeders believe +that long limbs are almost always accompanied by an elongated head. +Some instances of correlation are quite whimsical; thus cats with blue +eyes are invariably deaf; colour and constitutional peculiarities go +together, of which many remarkable cases could be given amongst +animals and plants. From the facts collected by Heusinger, it appears +that white sheep and pigs are differently affected from coloured +individuals by certain vegetable poisons. Hairless dogs have imperfect +teeth; long-haired and coarse-haired animals are apt to have, as is +asserted, long or many horns; pigeons with feathered feet have skin +between their outer toes; pigeons with short beaks have small feet, +and those with long beaks large feet. Hence, if man goes on selecting, +and thus augmenting, any peculiarity, he will almost certainly +unconsciously modify other parts of the structure, owing to the +mysterious laws of the correlation of growth. + +The result of the various, quite unknown, or dimly seen laws of +variation is infinitely complex and diversified. It is well worth +while carefully to study the several treatises published on some of +our old cultivated plants, as on the hyacinth, potato, even the +dahlia, etc.; and it is really surprising to note the endless points +in structure and constitution in which the varieties and sub-varieties +differ slightly from each other. The whole organisation seems to have +become plastic, and tends to depart in some small degree from that of +the parental type. + +Any variation which is not inherited is unimportant for us. But the +number and diversity of inheritable deviations of structure, both +those of slight and those of considerable physiological importance, is +endless. Dr. Prosper Lucas's treatise, in two large volumes, is the +fullest and the best on this subject. No breeder doubts how strong is +the tendency to inheritance: like produces like is his fundamental +belief: doubts have been thrown on this principle by theoretical +writers alone. When a deviation appears not unfrequently, and we see +it in the father and child, we cannot tell whether it may not be due +to the same original cause acting on both; but when amongst +individuals, apparently exposed to the same conditions, any very rare +deviation, due to some extraordinary combination of circumstances, +appears in the parent--say, once amongst several million +individuals--and it reappears in the child, the mere doctrine of +chances almost compels us to attribute its reappearance to +inheritance. Every one must have heard of cases of albinism, prickly +skin, hairy bodies, etc., appearing in several members of the same +family. If strange and rare deviations of structure are truly +inherited, less strange and commoner deviations may be freely admitted +to be inheritable. Perhaps the correct way of viewing the whole +subject, would be, to look at the inheritance of every character +whatever as the rule, and non-inheritance as the anomaly. + +The laws governing inheritance are quite unknown; no one can say why +the same peculiarity in different individuals of the same species, and +in individuals of different species, is sometimes inherited and +sometimes not so; why the child often reverts in certain characters to +its grandfather or grandmother or other much more remote ancestor; why +a peculiarity is often transmitted from one sex to both sexes or to +one sex alone, more commonly but not exclusively to the like sex. It +is a fact of some little importance to us, that peculiarities +appearing in the males of our domestic breeds are often transmitted +either exclusively, or in a much greater degree, to males alone. A +much more important rule, which I think may be trusted, is that, at +whatever period of life a peculiarity first appears, it tends to +appear in the offspring at a corresponding age, though sometimes +earlier. In many cases this could not be otherwise: thus the inherited +peculiarities in the horns of cattle could appear only in the +offspring when nearly mature; peculiarities in the silkworm are known +to appear at the corresponding caterpillar or cocoon stage. But +hereditary diseases and some other facts make me believe that the rule +has a wider extension, and that when there is no apparent reason why a +peculiarity should appear at any particular age, yet that it does tend +to appear in the offspring at the same period at which it first +appeared in the parent. I believe this rule to be of the highest +importance in explaining the laws of embryology. These remarks are of +course confined to the first APPEARANCE of the peculiarity, and not to +its primary cause, which may have acted on the ovules or male element; +in nearly the same manner as in the crossed offspring from a +short-horned cow by a long-horned bull, the greater length of horn, +though appearing late in life, is clearly due to the male element. + +Having alluded to the subject of reversion, I may here refer to a +statement often made by naturalists--namely, that our domestic +varieties, when run wild, gradually but certainly revert in character +to their aboriginal stocks. Hence it has been argued that no +deductions can be drawn from domestic races to species in a state of +nature. I have in vain endeavoured to discover on what decisive facts +the above statement has so often and so boldly been made. There would +be great difficulty in proving its truth: we may safely conclude that +very many of the most strongly-marked domestic varieties could not +possibly live in a wild state. In many cases we do not know what the +aboriginal stock was, and so could not tell whether or not nearly +perfect reversion had ensued. It would be quite necessary, in order to +prevent the effects of intercrossing, that only a single variety +should be turned loose in its new home. Nevertheless, as our varieties +certainly do occasionally revert in some of their characters to +ancestral forms, it seems to me not improbable, that if we could +succeed in naturalising, or were to cultivate, during many +generations, the several races, for instance, of the cabbage, in very +poor soil (in which case, however, some effect would have to be +attributed to the direct action of the poor soil), that they would to +a large extent, or even wholly, revert to the wild aboriginal stock. +Whether or not the experiment would succeed, is not of great +importance for our line of argument; for by the experiment itself the +conditions of life are changed. If it could be shown that our domestic +varieties manifested a strong tendency to reversion,--that is, to lose +their acquired characters, whilst kept under unchanged conditions, and +whilst kept in a considerable body, so that free intercrossing might +check, by blending together, any slight deviations of structure, in +such case, I grant that we could deduce nothing from domestic +varieties in regard to species. But there is not a shadow of evidence +in favour of this view: to assert that we could not breed our cart and +race-horses, long and short-horned cattle, and poultry of various +breeds, and esculent vegetables, for an almost infinite number of +generations, would be opposed to all experience. I may add, that when +under nature the conditions of life do change, variations and +reversions of character probably do occur; but natural selection, as +will hereafter be explained, will determine how far the new characters +thus arising shall be preserved. + +When we look to the hereditary varieties or races of our domestic +animals and plants, and compare them with species closely allied +together, we generally perceive in each domestic race, as already +remarked, less uniformity of character than in true species. Domestic +races of the same species, also, often have a somewhat monstrous +character; by which I mean, that, although differing from each other, +and from the other species of the same genus, in several trifling +respects, they often differ in an extreme degree in some one part, +both when compared one with another, and more especially when compared +with all the species in nature to which they are nearest allied. With +these exceptions (and with that of the perfect fertility of varieties +when crossed,--a subject hereafter to be discussed), domestic races of +the same species differ from each other in the same manner as, only in +most cases in a lesser degree than, do closely-allied species of the +same genus in a state of nature. I think this must be admitted, when +we find that there are hardly any domestic races, either amongst +animals or plants, which have not been ranked by some competent judges +as mere varieties, and by other competent judges as the descendants of +aboriginally distinct species. If any marked distinction existed +between domestic races and species, this source of doubt could not so +perpetually recur. It has often been stated that domestic races do not +differ from each other in characters of generic value. I think it +could be shown that this statement is hardly correct; but naturalists +differ most widely in determining what characters are of generic +value; all such valuations being at present empirical. Moreover, on +the view of the origin of genera which I shall presently give, we have +no right to expect often to meet with generic differences in our +domesticated productions. + +When we attempt to estimate the amount of structural difference +between the domestic races of the same species, we are soon involved +in doubt, from not knowing whether they have descended from one or +several parent-species. This point, if it could be cleared up, would +be interesting; if, for instance, it could be shown that the +greyhound, bloodhound, terrier, spaniel, and bull-dog, which we all +know propagate their kind so truly, were the offspring of any single +species, then such facts would have great weight in making us doubt +about the immutability of the many very closely allied and natural +species--for instance, of the many foxes--inhabiting different +quarters of the world. I do not believe, as we shall presently see, +that all our dogs have descended from any one wild species; but, in +the case of some other domestic races, there is presumptive, or even +strong, evidence in favour of this view. + +It has often been assumed that man has chosen for domestication +animals and plants having an extraordinary inherent tendency to vary, +and likewise to withstand diverse climates. I do not dispute that +these capacities have added largely to the value of most of our +domesticated productions; but how could a savage possibly know, when +he first tamed an animal, whether it would vary in succeeding +generations, and whether it would endure other climates? Has the +little variability of the ass or guinea-fowl, or the small power of +endurance of warmth by the rein-deer, or of cold by the common camel, +prevented their domestication? I cannot doubt that if other animals +and plants, equal in number to our domesticated productions, and +belonging to equally diverse classes and countries, were taken from a +state of nature, and could be made to breed for an equal number of +generations under domestication, they would vary on an average as +largely as the parent species of our existing domesticated productions +have varied. + +In the case of most of our anciently domesticated animals and plants, +I do not think it is possible to come to any definite conclusion, +whether they have descended from one or several species. The argument +mainly relied on by those who believe in the multiple origin of our +domestic animals is, that we find in the most ancient records, more +especially on the monuments of Egypt, much diversity in the breeds; +and that some of the breeds closely resemble, perhaps are identical +with, those still existing. Even if this latter fact were found more +strictly and generally true than seems to me to be the case, what does +it show, but that some of our breeds originated there, four or five +thousand years ago? But Mr. Horner's researches have rendered it in +some degree probable that man sufficiently civilized to have +manufactured pottery existed in the valley of the Nile thirteen or +fourteen thousand years ago; and who will pretend to say how long +before these ancient periods, savages, like those of Tierra del Fuego +or Australia, who possess a semi-domestic dog, may not have existed in +Egypt? + +The whole subject must, I think, remain vague; nevertheless, I may, +without here entering on any details, state that, from geographical +and other considerations, I think it highly probable that our domestic +dogs have descended from several wild species. In regard to sheep and +goats I can form no opinion. I should think, from facts communicated +to me by Mr. Blyth, on the habits, voice, and constitution, etc., of +the humped Indian cattle, that these had descended from a different +aboriginal stock from our European cattle; and several competent +judges believe that these latter have had more than one wild parent. +With respect to horses, from reasons which I cannot give here, I am +doubtfully inclined to believe, in opposition to several authors, that +all the races have descended from one wild stock. Mr. Blyth, whose +opinion, from his large and varied stores of knowledge, I should value +more than that of almost any one, thinks that all the breeds of +poultry have proceeded from the common wild Indian fowl (Gallus +bankiva). In regard to ducks and rabbits, the breeds of which differ +considerably from each other in structure, I do not doubt that they +all have descended from the common wild duck and rabbit. + +The doctrine of the origin of our several domestic races from several +aboriginal stocks, has been carried to an absurd extreme by some +authors. They believe that every race which breeds true, let the +distinctive characters be ever so slight, has had its wild prototype. +At this rate there must have existed at least a score of species of +wild cattle, as many sheep, and several goats in Europe alone, and +several even within Great Britain. One author believes that there +formerly existed in Great Britain eleven wild species of sheep +peculiar to it! When we bear in mind that Britain has now hardly one +peculiar mammal, and France but few distinct from those of Germany and +conversely, and so with Hungary, Spain, etc., but that each of these +kingdoms possesses several peculiar breeds of cattle, sheep, etc., we +must admit that many domestic breeds have originated in Europe; for +whence could they have been derived, as these several countries do not +possess a number of peculiar species as distinct parent-stocks? So it +is in India. Even in the case of the domestic dogs of the whole world, +which I fully admit have probably descended from several wild species, +I cannot doubt that there has been an immense amount of inherited +variation. Who can believe that animals closely resembling the Italian +greyhound, the bloodhound, the bull-dog, or Blenheim spaniel, etc.--so +unlike all wild Canidae--ever existed freely in a state of nature? It +has often been loosely said that all our races of dogs have been +produced by the crossing of a few aboriginal species; but by crossing +we can get only forms in some degree intermediate between their +parents; and if we account for our several domestic races by this +process, we must admit the former existence of the most extreme forms, +as the Italian greyhound, bloodhound, bull-dog, etc., in the wild +state. Moreover, the possibility of making distinct races by crossing +has been greatly exaggerated. There can be no doubt that a race may be +modified by occasional crosses, if aided by the careful selection of +those individual mongrels, which present any desired character; but +that a race could be obtained nearly intermediate between two +extremely different races or species, I can hardly believe. Sir J. +Sebright expressly experimentised for this object, and failed. The +offspring from the first cross between two pure breeds is tolerably +and sometimes (as I have found with pigeons) extremely uniform, and +everything seems simple enough; but when these mongrels are crossed +one with another for several generations, hardly two of them will be +alike, and then the extreme difficulty, or rather utter hopelessness, +of the task becomes apparent. Certainly, a breed intermediate between +TWO VERY DISTINCT breeds could not be got without extreme care and +long-continued selection; nor can I find a single case on record of a +permanent race having been thus formed. + +ON THE BREEDS OF THE DOMESTIC PIGEON. + +Believing that it is always best to study some special group, I have, +after deliberation, taken up domestic pigeons. I have kept every breed +which I could purchase or obtain, and have been most kindly favoured +with skins from several quarters of the world, more especially by the +Honourable W. Elliot from India, and by the Honourable C. Murray from +Persia. Many treatises in different languages have been published on +pigeons, and some of them are very important, as being of considerable +antiquity. I have associated with several eminent fanciers, and have +been permitted to join two of the London Pigeon Clubs. The diversity +of the breeds is something astonishing. Compare the English carrier +and the short-faced tumbler, and see the wonderful difference in their +beaks, entailing corresponding differences in their skulls. The +carrier, more especially the male bird, is also remarkable from the +wonderful development of the carunculated skin about the head, and +this is accompanied by greatly elongated eyelids, very large external +orifices to the nostrils, and a wide gape of mouth. The short-faced +tumbler has a beak in outline almost like that of a finch; and the +common tumbler has the singular and strictly inherited habit of flying +at a great height in a compact flock, and tumbling in the air head +over heels. The runt is a bird of great size, with long, massive beak +and large feet; some of the sub-breeds of runts have very long necks, +others very long wings and tails, others singularly short tails. The +barb is allied to the carrier, but, instead of a very long beak, has a +very short and very broad one. The pouter has a much elongated body, +wings, and legs; and its enormously developed crop, which it glories +in inflating, may well excite astonishment and even laughter. The +turbit has a very short and conical beak, with a line of reversed +feathers down the breast; and it has the habit of continually +expanding slightly the upper part of the oesophagus. The Jacobin has +the feathers so much reversed along the back of the neck that they +form a hood, and it has, proportionally to its size, much elongated +wing and tail feathers. The trumpeter and laugher, as their names +express, utter a very different coo from the other breeds. The fantail +has thirty or even forty tail-feathers, instead of twelve or fourteen, +the normal number in all members of the great pigeon family; and these +feathers are kept expanded, and are carried so erect that in good +birds the head and tail touch; the oil-gland is quite aborted. Several +other less distinct breeds might have been specified. + +In the skeletons of the several breeds, the development of the bones +of the face in length and breadth and curvature differs enormously. +The shape, as well as the breadth and length of the ramus of the lower +jaw, varies in a highly remarkable manner. The number of the caudal +and sacral vertebrae vary; as does the number of the ribs, together +with their relative breadth and the presence of processes. The size +and shape of the apertures in the sternum are highly variable; so is +the degree of divergence and relative size of the two arms of the +furcula. The proportional width of the gape of mouth, the proportional +length of the eyelids, of the orifice of the nostrils, of the tongue +(not always in strict correlation with the length of beak), the size +of the crop and of the upper part of the oesophagus; the development +and abortion of the oil-gland; the number of the primary wing and +caudal feathers; the relative length of wing and tail to each other +and to the body; the relative length of leg and of the feet; the +number of scutellae on the toes, the development of skin between the +toes, are all points of structure which are variable. The period at +which the perfect plumage is acquired varies, as does the state of the +down with which the nestling birds are clothed when hatched. The shape +and size of the eggs vary. The manner of flight differs remarkably; as +does in some breeds the voice and disposition. Lastly, in certain +breeds, the males and females have come to differ to a slight degree +from each other. + +Altogether at least a score of pigeons might be chosen, which if shown +to an ornithologist, and he were told that they were wild birds, would +certainly, I think, be ranked by him as well-defined species. +Moreover, I do not believe that any ornithologist would place the +English carrier, the short-faced tumbler, the runt, the barb, pouter, +and fantail in the same genus; more especially as in each of these +breeds several truly-inherited sub-breeds, or species as he might have +called them, could be shown him. + +Great as the differences are between the breeds of pigeons, I am fully +convinced that the common opinion of naturalists is correct, namely, +that all have descended from the rock-pigeon (Columba livia), +including under this term several geographical races or sub-species, +which differ from each other in the most trifling respects. As several +of the reasons which have led me to this belief are in some degree +applicable in other cases, I will here briefly give them. If the +several breeds are not varieties, and have not proceeded from the +rock-pigeon, they must have descended from at least seven or eight +aboriginal stocks; for it is impossible to make the present domestic +breeds by the crossing of any lesser number: how, for instance, could +a pouter be produced by crossing two breeds unless one of the +parent-stocks possessed the characteristic enormous crop? The supposed +aboriginal stocks must all have been rock-pigeons, that is, not +breeding or willingly perching on trees. But besides C. livia, with +its geographical sub-species, only two or three other species of +rock-pigeons are known; and these have not any of the characters of +the domestic breeds. Hence the supposed aboriginal stocks must either +still exist in the countries where they were originally domesticated, +and yet be unknown to ornithologists; and this, considering their +size, habits, and remarkable characters, seems very improbable; or +they must have become extinct in the wild state. But birds breeding on +precipices, and good fliers, are unlikely to be exterminated; and the +common rock-pigeon, which has the same habits with the domestic +breeds, has not been exterminated even on several of the smaller +British islets, or on the shores of the Mediterranean. Hence the +supposed extermination of so many species having similar habits with +the rock-pigeon seems to me a very rash assumption. Moreover, the +several above-named domesticated breeds have been transported to all +parts of the world, and, therefore, some of them must have been +carried back again into their native country; but not one has ever +become wild or feral, though the dovecot-pigeon, which is the +rock-pigeon in a very slightly altered state, has become feral in +several places. Again, all recent experience shows that it is most +difficult to get any wild animal to breed freely under domestication; +yet on the hypothesis of the multiple origin of our pigeons, it must +be assumed that at least seven or eight species were so thoroughly +domesticated in ancient times by half-civilized man, as to be quite +prolific under confinement. + +An argument, as it seems to me, of great weight, and applicable in +several other cases, is, that the above-specified breeds, though +agreeing generally in constitution, habits, voice, colouring, and in +most parts of their structure, with the wild rock-pigeon, yet are +certainly highly abnormal in other parts of their structure: we may +look in vain throughout the whole great family of Columbidae for a +beak like that of the English carrier, or that of the short-faced +tumbler, or barb; for reversed feathers like those of the jacobin; for +a crop like that of the pouter; for tail-feathers like those of the +fantail. Hence it must be assumed not only that half-civilized man +succeeded in thoroughly domesticating several species, but that he +intentionally or by chance picked out extraordinarily abnormal +species; and further, that these very species have since all become +extinct or unknown. So many strange contingencies seem to me +improbable in the highest degree. + +Some facts in regard to the colouring of pigeons well deserve +consideration. The rock-pigeon is of a slaty-blue, and has a white +rump (the Indian sub-species, C. intermedia of Strickland, having it +bluish); the tail has a terminal dark bar, with the bases of the outer +feathers externally edged with white; the wings have two black bars; +some semi-domestic breeds and some apparently truly wild breeds have, +besides the two black bars, the wings chequered with black. These +several marks do not occur together in any other species of the whole +family. Now, in every one of the domestic breeds, taking thoroughly +well-bred birds, all the above marks, even to the white edging of the +outer tail-feathers, sometimes concur perfectly developed. Moreover, +when two birds belonging to two distinct breeds are crossed, neither +of which is blue or has any of the above-specified marks, the mongrel +offspring are very apt suddenly to acquire these characters; for +instance, I crossed some uniformly white fantails with some uniformly +black barbs, and they produced mottled brown and black birds; these I +again crossed together, and one grandchild of the pure white fantail +and pure black barb was of as beautiful a blue colour, with the white +rump, double black wing-bar, and barred and white-edged tail-feathers, +as any wild rock-pigeon! We can understand these facts, on the +well-known principle of reversion to ancestral characters, if all the +domestic breeds have descended from the rock-pigeon. But if we deny +this, we must make one of the two following highly improbable +suppositions. Either, firstly, that all the several imagined +aboriginal stocks were coloured and marked like the rock-pigeon, +although no other existing species is thus coloured and marked, so +that in each separate breed there might be a tendency to revert to the +very same colours and markings. Or, secondly, that each breed, even +the purest, has within a dozen or, at most, within a score of +generations, been crossed by the rock-pigeon: I say within a dozen or +twenty generations, for we know of no fact countenancing the belief +that the child ever reverts to some one ancestor, removed by a greater +number of generations. In a breed which has been crossed only once +with some distinct breed, the tendency to reversion to any character +derived from such cross will naturally become less and less, as in +each succeeding generation there will be less of the foreign blood; +but when there has been no cross with a distinct breed, and there is a +tendency in both parents to revert to a character, which has been lost +during some former generation, this tendency, for all that we can see +to the contrary, may be transmitted undiminished for an indefinite +number of generations. These two distinct cases are often confounded +in treatises on inheritance. + +Lastly, the hybrids or mongrels from between all the domestic breeds +of pigeons are perfectly fertile. I can state this from my own +observations, purposely made on the most distinct breeds. Now, it is +difficult, perhaps impossible, to bring forward one case of the hybrid +offspring of two animals CLEARLY DISTINCT being themselves perfectly +fertile. Some authors believe that long-continued domestication +eliminates this strong tendency to sterility: from the history of the +dog I think there is some probability in this hypothesis, if applied +to species closely related together, though it is unsupported by a +single experiment. But to extend the hypothesis so far as to suppose +that species, aboriginally as distinct as carriers, tumblers, pouters, +and fantails now are, should yield offspring perfectly fertile, inter +se, seems to me rash in the extreme. + +From these several reasons, namely, the improbability of man having +formerly got seven or eight supposed species of pigeons to breed +freely under domestication; these supposed species being quite unknown +in a wild state, and their becoming nowhere feral; these species +having very abnormal characters in certain respects, as compared with +all other Columbidae, though so like in most other respects to the +rock-pigeon; the blue colour and various marks occasionally appearing +in all the breeds, both when kept pure and when crossed; the mongrel +offspring being perfectly fertile;--from these several reasons, taken +together, I can feel no doubt that all our domestic breeds have +descended from the Columba livia with its geographical sub-species. + +In favour of this view, I may add, firstly, that C. livia, or the +rock-pigeon, has been found capable of domestication in Europe and in +India; and that it agrees in habits and in a great number of points of +structure with all the domestic breeds. Secondly, although an English +carrier or short-faced tumbler differs immensely in certain characters +from the rock-pigeon, yet by comparing the several sub-breeds of these +breeds, more especially those brought from distant countries, we can +make an almost perfect series between the extremes of structure. +Thirdly, those characters which are mainly distinctive of each breed, +for instance the wattle and length of beak of the carrier, the +shortness of that of the tumbler, and the number of tail-feathers in +the fantail, are in each breed eminently variable; and the explanation +of this fact will be obvious when we come to treat of selection. +Fourthly, pigeons have been watched, and tended with the utmost care, +and loved by many people. They have been domesticated for thousands of +years in several quarters of the world; the earliest known record of +pigeons is in the fifth Aegyptian dynasty, about 3000 B.C., as was +pointed out to me by Professor Lepsius; but Mr. Birch informs me that +pigeons are given in a bill of fare in the previous dynasty. In the +time of the Romans, as we hear from Pliny, immense prices were given +for pigeons; "nay, they are come to this pass, that they can reckon up +their pedigree and race." Pigeons were much valued by Akber Khan in +India, about the year 1600; never less than 20,000 pigeons were taken +with the court. "The monarchs of Iran and Turan sent him some very +rare birds;" and, continues the courtly historian, "His Majesty by +crossing the breeds, which method was never practised before, has +improved them astonishingly." About this same period the Dutch were as +eager about pigeons as were the old Romans. The paramount importance +of these considerations in explaining the immense amount of variation +which pigeons have undergone, will be obvious when we treat of +Selection. We shall then, also, see how it is that the breeds so often +have a somewhat monstrous character. It is also a most favourable +circumstance for the production of distinct breeds, that male and +female pigeons can be easily mated for life; and thus different breeds +can be kept together in the same aviary. + +I have discussed the probable origin of domestic pigeons at some, yet +quite insufficient, length; because when I first kept pigeons and +watched the several kinds, knowing well how true they bred, I felt +fully as much difficulty in believing that they could ever have +descended from a common parent, as any naturalist could in coming to a +similar conclusion in regard to the many species of finches, or other +large groups of birds, in nature. One circumstance has struck me much; +namely, that all the breeders of the various domestic animals and the +cultivators of plants, with whom I have ever conversed, or whose +treatises I have read, are firmly convinced that the several breeds to +which each has attended, are descended from so many aboriginally +distinct species. Ask, as I have asked, a celebrated raiser of +Hereford cattle, whether his cattle might not have descended from long +horns, and he will laugh you to scorn. I have never met a pigeon, or +poultry, or duck, or rabbit fancier, who was not fully convinced that +each main breed was descended from a distinct species. Van Mons, in +his treatise on pears and apples, shows how utterly he disbelieves +that the several sorts, for instance a Ribston-pippin or Codlin-apple, +could ever have proceeded from the seeds of the same tree. Innumerable +other examples could be given. The explanation, I think, is simple: +from long-continued study they are strongly impressed with the +differences between the several races; and though they well know that +each race varies slightly, for they win their prizes by selecting such +slight differences, yet they ignore all general arguments, and refuse +to sum up in their minds slight differences accumulated during many +successive generations. May not those naturalists who, knowing far +less of the laws of inheritance than does the breeder, and knowing no +more than he does of the intermediate links in the long lines of +descent, yet admit that many of our domestic races have descended from +the same parents--may they not learn a lesson of caution, when they +deride the idea of species in a state of nature being lineal +descendants of other species? + +SELECTION. + +Let us now briefly consider the steps by which domestic races have +been produced, either from one or from several allied species. Some +little effect may, perhaps, be attributed to the direct action of the +external conditions of life, and some little to habit; but he would be +a bold man who would account by such agencies for the differences of a +dray and race horse, a greyhound and bloodhound, a carrier and tumbler +pigeon. One of the most remarkable features in our domesticated races +is that we see in them adaptation, not indeed to the animal's or +plant's own good, but to man's use or fancy. Some variations useful to +him have probably arisen suddenly, or by one step; many botanists, for +instance, believe that the fuller's teazle, with its hooks, which +cannot be rivalled by any mechanical contrivance, is only a variety of +the wild Dipsacus; and this amount of change may have suddenly arisen +in a seedling. So it has probably been with the turnspit dog; and this +is known to have been the case with the ancon sheep. But when we +compare the dray-horse and race-horse, the dromedary and camel, the +various breeds of sheep fitted either for cultivated land or mountain +pasture, with the wool of one breed good for one purpose, and that of +another breed for another purpose; when we compare the many breeds of +dogs, each good for man in very different ways; when we compare the +game-cock, so pertinacious in battle, with other breeds so little +quarrelsome, with "everlasting layers" which never desire to sit, and +with the bantam so small and elegant; when we compare the host of +agricultural, culinary, orchard, and flower-garden races of plants, +most useful to man at different seasons and for different purposes, or +so beautiful in his eyes, we must, I think, look further than to mere +variability. We cannot suppose that all the breeds were suddenly +produced as perfect and as useful as we now see them; indeed, in +several cases, we know that this has not been their history. The key +is man's power of accumulative selection: nature gives successive +variations; man adds them up in certain directions useful to him. In +this sense he may be said to make for himself useful breeds. + +The great power of this principle of selection is not hypothetical. It +is certain that several of our eminent breeders have, even within a +single lifetime, modified to a large extent some breeds of cattle and +sheep. In order fully to realise what they have done, it is almost +necessary to read several of the many treatises devoted to this +subject, and to inspect the animals. Breeders habitually speak of an +animal's organisation as something quite plastic, which they can model +almost as they please. If I had space I could quote numerous passages +to this effect from highly competent authorities. Youatt, who was +probably better acquainted with the works of agriculturalists than +almost any other individual, and who was himself a very good judge of +an animal, speaks of the principle of selection as "that which enables +the agriculturist, not only to modify the character of his flock, but +to change it altogether. It is the magician's wand, by means of which +he may summon into life whatever form and mould he pleases." Lord +Somerville, speaking of what breeders have done for sheep, says:--"It +would seem as if they had chalked out upon a wall a form perfect in +itself, and then had given it existence." That most skilful breeder, +Sir John Sebright, used to say, with respect to pigeons, that "he +would produce any given feather in three years, but it would take him +six years to obtain head and beak." In Saxony the importance of the +principle of selection in regard to merino sheep is so fully +recognised, that men follow it as a trade: the sheep are placed on a +table and are studied, like a picture by a connoisseur; this is done +three times at intervals of months, and the sheep are each time marked +and classed, so that the very best may ultimately be selected for +breeding. + +What English breeders have actually effected is proved by the enormous +prices given for animals with a good pedigree; and these have now been +exported to almost every quarter of the world. The improvement is by +no means generally due to crossing different breeds; all the best +breeders are strongly opposed to this practice, except sometimes +amongst closely allied sub-breeds. And when a cross has been made, the +closest selection is far more indispensable even than in ordinary +cases. If selection consisted merely in separating some very distinct +variety, and breeding from it, the principle would be so obvious as +hardly to be worth notice; but its importance consists in the great +effect produced by the accumulation in one direction, during +successive generations, of differences absolutely inappreciable by an +uneducated eye--differences which I for one have vainly attempted to +appreciate. Not one man in a thousand has accuracy of eye and judgment +sufficient to become an eminent breeder. If gifted with these +qualities, and he studies his subject for years, and devotes his +lifetime to it with indomitable perseverance, he will succeed, and may +make great improvements; if he wants any of these qualities, he will +assuredly fail. Few would readily believe in the natural capacity and +years of practice requisite to become even a skilful pigeon-fancier. + +The same principles are followed by horticulturists; but the +variations are here often more abrupt. No one supposes that our +choicest productions have been produced by a single variation from the +aboriginal stock. We have proofs that this is not so in some cases, in +which exact records have been kept; thus, to give a very trifling +instance, the steadily-increasing size of the common gooseberry may be +quoted. We see an astonishing improvement in many florists' flowers, +when the flowers of the present day are compared with drawings made +only twenty or thirty years ago. When a race of plants is once pretty +well established, the seed-raisers do not pick out the best plants, +but merely go over their seed-beds, and pull up the "rogues," as they +call the plants that deviate from the proper standard. With animals +this kind of selection is, in fact, also followed; for hardly any one +is so careless as to allow his worst animals to breed. + +In regard to plants, there is another means of observing the +accumulated effects of selection--namely, by comparing the diversity +of flowers in the different varieties of the same species in the +flower-garden; the diversity of leaves, pods, or tubers, or whatever +part is valued, in the kitchen-garden, in comparison with the flowers +of the same varieties; and the diversity of fruit of the same species +in the orchard, in comparison with the leaves and flowers of the same +set of varieties. See how different the leaves of the cabbage are, and +how extremely alike the flowers; how unlike the flowers of the +heartsease are, and how alike the leaves; how much the fruit of the +different kinds of gooseberries differ in size, colour, shape, and +hairiness, and yet the flowers present very slight differences. It is +not that the varieties which differ largely in some one point do not +differ at all in other points; this is hardly ever, perhaps never, the +case. The laws of correlation of growth, the importance of which +should never be overlooked, will ensure some differences; but, as a +general rule, I cannot doubt that the continued selection of slight +variations, either in the leaves, the flowers, or the fruit, will +produce races differing from each other chiefly in these characters. + +It may be objected that the principle of selection has been reduced to +methodical practice for scarcely more than three-quarters of a +century; it has certainly been more attended to of late years, and +many treatises have been published on the subject; and the result, I +may add, has been, in a corresponding degree, rapid and important. But +it is very far from true that the principle is a modern discovery. I +could give several references to the full acknowledgment of the +importance of the principle in works of high antiquity. In rude and +barbarous periods of English history choice animals were often +imported, and laws were passed to prevent their exportation: the +destruction of horses under a certain size was ordered, and this may +be compared to the "roguing" of plants by nurserymen. The principle of +selection I find distinctly given in an ancient Chinese encyclopaedia. +Explicit rules are laid down by some of the Roman classical writers. +From passages in Genesis, it is clear that the colour of domestic +animals was at that early period attended to. Savages now sometimes +cross their dogs with wild canine animals, to improve the breed, and +they formerly did so, as is attested by passages in Pliny. The savages +in South Africa match their draught cattle by colour, as do some of +the Esquimaux their teams of dogs. Livingstone shows how much good +domestic breeds are valued by the negroes of the interior of Africa +who have not associated with Europeans. Some of these facts do not +show actual selection, but they show that the breeding of domestic +animals was carefully attended to in ancient times, and is now +attended to by the lowest savages. It would, indeed, have been a +strange fact, had attention not been paid to breeding, for the +inheritance of good and bad qualities is so obvious. + +At the present time, eminent breeders try by methodical selection, +with a distinct object in view, to make a new strain or sub-breed, +superior to anything existing in the country. But, for our purpose, a +kind of Selection, which may be called Unconscious, and which results +from every one trying to possess and breed from the best individual +animals, is more important. Thus, a man who intends keeping pointers +naturally tries to get as good dogs as he can, and afterwards breeds +from his own best dogs, but he has no wish or expectation of +permanently altering the breed. Nevertheless I cannot doubt that this +process, continued during centuries, would improve and modify any +breed, in the same way as Bakewell, Collins, etc., by this very same +process, only carried on more methodically, did greatly modify, even +during their own lifetimes, the forms and qualities of their cattle. +Slow and insensible changes of this kind could never be recognised +unless actual measurements or careful drawings of the breeds in +question had been made long ago, which might serve for comparison. In +some cases, however, unchanged or but little changed individuals of +the same breed may be found in less civilised districts, where the +breed has been less improved. There is reason to believe that King +Charles's spaniel has been unconsciously modified to a large extent +since the time of that monarch. Some highly competent authorities are +convinced that the setter is directly derived from the spaniel, and +has probably been slowly altered from it. It is known that the English +pointer has been greatly changed within the last century, and in this +case the change has, it is believed, been chiefly effected by crosses +with the fox-hound; but what concerns us is, that the change has been +effected unconsciously and gradually, and yet so effectually, that, +though the old Spanish pointer certainly came from Spain, Mr. Borrow +has not seen, as I am informed by him, any native dog in Spain like +our pointer. + +By a similar process of selection, and by careful training, the whole +body of English racehorses have come to surpass in fleetness and size +the parent Arab stock, so that the latter, by the regulations for the +Goodwood Races, are favoured in the weights they carry. Lord Spencer +and others have shown how the cattle of England have increased in +weight and in early maturity, compared with the stock formerly kept in +this country. By comparing the accounts given in old pigeon treatises +of carriers and tumblers with these breeds as now existing in Britain, +India, and Persia, we can, I think, clearly trace the stages through +which they have insensibly passed, and come to differ so greatly from +the rock-pigeon. + +Youatt gives an excellent illustration of the effects of a course of +selection, which may be considered as unconsciously followed, in so +far that the breeders could never have expected or even have wished to +have produced the result which ensued--namely, the production of two +distinct strains. The two flocks of Leicester sheep kept by Mr. +Buckley and Mr. Burgess, as Mr. Youatt remarks, "have been purely bred +from the original stock of Mr. Bakewell for upwards of fifty years. +There is not a suspicion existing in the mind of any one at all +acquainted with the subject that the owner of either of them has +deviated in any one instance from the pure blood of Mr. Bakewell's +flock, and yet the difference between the sheep possessed by these two +gentlemen is so great that they have the appearance of being quite +different varieties." + +If there exist savages so barbarous as never to think of the inherited +character of the offspring of their domestic animals, yet any one +animal particularly useful to them, for any special purpose, would be +carefully preserved during famines and other accidents, to which +savages are so liable, and such choice animals would thus generally +leave more offspring than the inferior ones; so that in this case +there would be a kind of unconscious selection going on. We see the +value set on animals even by the barbarians of Tierra del Fuego, by +their killing and devouring their old women, in times of dearth, as of +less value than their dogs. + +In plants the same gradual process of improvement, through the +occasional preservation of the best individuals, whether or not +sufficiently distinct to be ranked at their first appearance as +distinct varieties, and whether or not two or more species or races +have become blended together by crossing, may plainly be recognised in +the increased size and beauty which we now see in the varieties of the +heartsease, rose, pelargonium, dahlia, and other plants, when compared +with the older varieties or with their parent-stocks. No one would +ever expect to get a first-rate heartsease or dahlia from the seed of +a wild plant. No one would expect to raise a first-rate melting pear +from the seed of a wild pear, though he might succeed from a poor +seedling growing wild, if it had come from a garden-stock. The pear, +though cultivated in classical times, appears, from Pliny's +description, to have been a fruit of very inferior quality. I have +seen great surprise expressed in horticultural works at the wonderful +skill of gardeners, in having produced such splendid results from such +poor materials; but the art, I cannot doubt, has been simple, and, as +far as the final result is concerned, has been followed almost +unconsciously. It has consisted in always cultivating the best known +variety, sowing its seeds, and, when a slightly better variety has +chanced to appear, selecting it, and so onwards. But the gardeners of +the classical period, who cultivated the best pear they could procure, +never thought what splendid fruit we should eat; though we owe our +excellent fruit, in some small degree, to their having naturally +chosen and preserved the best varieties they could anywhere find. + +A large amount of change in our cultivated plants, thus slowly and +unconsciously accumulated, explains, as I believe, the well-known +fact, that in a vast number of cases we cannot recognise, and +therefore do not know, the wild parent-stocks of the plants which have +been longest cultivated in our flower and kitchen gardens. If it has +taken centuries or thousands of years to improve or modify most of our +plants up to their present standard of usefulness to man, we can +understand how it is that neither Australia, the Cape of Good Hope, +nor any other region inhabited by quite uncivilised man, has afforded +us a single plant worth culture. It is not that these countries, so +rich in species, do not by a strange chance possess the aboriginal +stocks of any useful plants, but that the native plants have not been +improved by continued selection up to a standard of perfection +comparable with that given to the plants in countries anciently +civilised. + +In regard to the domestic animals kept by uncivilised man, it should +not be overlooked that they almost always have to struggle for their +own food, at least during certain seasons. And in two countries very +differently circumstanced, individuals of the same species, having +slightly different constitutions or structure, would often succeed +better in the one country than in the other, and thus by a process of +"natural selection," as will hereafter be more fully explained, two +sub-breeds might be formed. This, perhaps, partly explains what has +been remarked by some authors, namely, that the varieties kept by +savages have more of the character of species than the varieties kept +in civilised countries. + +On the view here given of the all-important part which selection by +man has played, it becomes at once obvious, how it is that our +domestic races show adaptation in their structure or in their habits +to man's wants or fancies. We can, I think, further understand the +frequently abnormal character of our domestic races, and likewise +their differences being so great in external characters and relatively +so slight in internal parts or organs. Man can hardly select, or only +with much difficulty, any deviation of structure excepting such as is +externally visible; and indeed he rarely cares for what is internal. +He can never act by selection, excepting on variations which are first +given to him in some slight degree by nature. No man would ever try to +make a fantail, till he saw a pigeon with a tail developed in some +slight degree in an unusual manner, or a pouter till he saw a pigeon +with a crop of somewhat unusual size; and the more abnormal or unusual +any character was when it first appeared, the more likely it would be +to catch his attention. But to use such an expression as trying to +make a fantail, is, I have no doubt, in most cases, utterly incorrect. +The man who first selected a pigeon with a slightly larger tail, never +dreamed what the descendants of that pigeon would become through +long-continued, partly unconscious and partly methodical selection. +Perhaps the parent bird of all fantails had only fourteen +tail-feathers somewhat expanded, like the present Java fantail, or +like individuals of other and distinct breeds, in which as many as +seventeen tail-feathers have been counted. Perhaps the first +pouter-pigeon did not inflate its crop much more than the turbit now +does the upper part of its oesophagus,--a habit which is disregarded +by all fanciers, as it is not one of the points of the breed. + +Nor let it be thought that some great deviation of structure would be +necessary to catch the fancier's eye: he perceives extremely small +differences, and it is in human nature to value any novelty, however +slight, in one's own possession. Nor must the value which would +formerly be set on any slight differences in the individuals of the +same species, be judged of by the value which would now be set on +them, after several breeds have once fairly been established. Many +slight differences might, and indeed do now, arise amongst pigeons, +which are rejected as faults or deviations from the standard of +perfection of each breed. The common goose has not given rise to any +marked varieties; hence the Thoulouse and the common breed, which +differ only in colour, that most fleeting of characters, have lately +been exhibited as distinct at our poultry-shows. + +I think these views further explain what has sometimes been +noticed--namely that we know nothing about the origin or history of +any of our domestic breeds. But, in fact, a breed, like a dialect of a +language, can hardly be said to have had a definite origin. A man +preserves and breeds from an individual with some slight deviation of +structure, or takes more care than usual in matching his best animals +and thus improves them, and the improved individuals slowly spread in +the immediate neighbourhood. But as yet they will hardly have a +distinct name, and from being only slightly valued, their history will +be disregarded. When further improved by the same slow and gradual +process, they will spread more widely, and will get recognised as +something distinct and valuable, and will then probably first receive +a provincial name. In semi-civilised countries, with little free +communication, the spreading and knowledge of any new sub-breed will +be a slow process. As soon as the points of value of the new sub-breed +are once fully acknowledged, the principle, as I have called it, of +unconscious selection will always tend,--perhaps more at one period +than at another, as the breed rises or falls in fashion,--perhaps more +in one district than in another, according to the state of +civilisation of the inhabitants--slowly to add to the characteristic +features of the breed, whatever they may be. But the chance will be +infinitely small of any record having been preserved of such slow, +varying, and insensible changes. + +I must now say a few words on the circumstances, favourable, or the +reverse, to man's power of selection. A high degree of variability is +obviously favourable, as freely giving the materials for selection to +work on; not that mere individual differences are not amply +sufficient, with extreme care, to allow of the accumulation of a large +amount of modification in almost any desired direction. But as +variations manifestly useful or pleasing to man appear only +occasionally, the chance of their appearance will be much increased by +a large number of individuals being kept; and hence this comes to be +of the highest importance to success. On this principle Marshall has +remarked, with respect to the sheep of parts of Yorkshire, that "as +they generally belong to poor people, and are mostly IN SMALL LOTS, +they never can be improved." On the other hand, nurserymen, from +raising large stocks of the same plants, are generally far more +successful than amateurs in getting new and valuable varieties. The +keeping of a large number of individuals of a species in any country +requires that the species should be placed under favourable conditions +of life, so as to breed freely in that country. When the individuals +of any species are scanty, all the individuals, whatever their quality +may be, will generally be allowed to breed, and this will effectually +prevent selection. But probably the most important point of all, is, +that the animal or plant should be so highly useful to man, or so much +valued by him, that the closest attention should be paid to even the +slightest deviation in the qualities or structure of each individual. +Unless such attention be paid nothing can be effected. I have seen it +gravely remarked, that it was most fortunate that the strawberry began +to vary just when gardeners began to attend closely to this plant. No +doubt the strawberry had always varied since it was cultivated, but +the slight varieties had been neglected. As soon, however, as +gardeners picked out individual plants with slightly larger, earlier, +or better fruit, and raised seedlings from them, and again picked out +the best seedlings and bred from them, then, there appeared (aided by +some crossing with distinct species) those many admirable varieties of +the strawberry which have been raised during the last thirty or forty +years. + +In the case of animals with separate sexes, facility in preventing +crosses is an important element of success in the formation of new +races,--at least, in a country which is already stocked with other +races. In this respect enclosure of the land plays a part. Wandering +savages or the inhabitants of open plains rarely possess more than one +breed of the same species. Pigeons can be mated for life, and this is +a great convenience to the fancier, for thus many races may be kept +true, though mingled in the same aviary; and this circumstance must +have largely favoured the improvement and formation of new breeds. +Pigeons, I may add, can be propagated in great numbers and at a very +quick rate, and inferior birds may be freely rejected, as when killed +they serve for food. On the other hand, cats, from their nocturnal +rambling habits, cannot be matched, and, although so much valued by +women and children, we hardly ever see a distinct breed kept up; such +breeds as we do sometimes see are almost always imported from some +other country, often from islands. Although I do not doubt that some +domestic animals vary less than others, yet the rarity or absence of +distinct breeds of the cat, the donkey, peacock, goose, etc., may be +attributed in main part to selection not having been brought into +play: in cats, from the difficulty in pairing them; in donkeys, from +only a few being kept by poor people, and little attention paid to +their breeding; in peacocks, from not being very easily reared and a +large stock not kept; in geese, from being valuable only for two +purposes, food and feathers, and more especially from no pleasure +having been felt in the display of distinct breeds. + +To sum up on the origin of our Domestic Races of animals and plants. I +believe that the conditions of life, from their action on the +reproductive system, are so far of the highest importance as causing +variability. I do not believe that variability is an inherent and +necessary contingency, under all circumstances, with all organic +beings, as some authors have thought. The effects of variability are +modified by various degrees of inheritance and of reversion. +Variability is governed by many unknown laws, more especially by that +of correlation of growth. Something may be attributed to the direct +action of the conditions of life. Something must be attributed to use +and disuse. The final result is thus rendered infinitely complex. In +some cases, I do not doubt that the intercrossing of species, +aboriginally distinct, has played an important part in the origin of +our domestic productions. When in any country several domestic breeds +have once been established, their occasional intercrossing, with the +aid of selection, has, no doubt, largely aided in the formation of new +sub-breeds; but the importance of the crossing of varieties has, I +believe, been greatly exaggerated, both in regard to animals and to +those plants which are propagated by seed. In plants which are +temporarily propagated by cuttings, buds, etc., the importance of the +crossing both of distinct species and of varieties is immense; for the +cultivator here quite disregards the extreme variability both of +hybrids and mongrels, and the frequent sterility of hybrids; but the +cases of plants not propagated by seed are of little importance to us, +for their endurance is only temporary. Over all these causes of Change +I am convinced that the accumulative action of Selection, whether +applied methodically and more quickly, or unconsciously and more +slowly, but more efficiently, is by far the predominant Power. + + Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/PackageTest.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/PackageTest.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/PackageTest.java Wed Mar 4 21:05:53 2009 @@ -15,6 +15,6 @@ @RunWith(Suite.class) -(a)SuiteClasses({RandomUtilTest.class}) +@SuiteClasses({}) public class PackageTest { } \ No newline at end of file Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/ScenarioRandomUtil.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/ScenarioRandomUtil.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/control/ScenarioRandomUtil.java Wed Mar 4 21:05:53 2009 @@ -1,17 +1,18 @@ -/** - * LOGBack: the reliable, fast and flexible logging library for Java. - * - * Copyright (C) 1999-2005, QOS.ch, LOGBack.com - * - * This library is free software, you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public License as - * published by the Free Software Foundation. +/** + * Logback: the generic, reliable, fast and flexible logging framework. + * + * Copyright (C) 2000-2009, QOS.ch + * + * This library is free software, you can redistribute it and/or modify it under + * the terms of the GNU Lesser General Public License as published by the Free + * Software Foundation. */ package ch.qos.logback.classic.control; import java.util.Random; import ch.qos.logback.classic.Level; +import ch.qos.logback.classic.corpus.RandomUtil; public class ScenarioRandomUtil { private final static long SEED = 74130; @@ -49,7 +50,7 @@ } public static String randomLoggerName(int average, int stdDeviation) { - int depth = gaussianAsPositiveInt(average, stdDeviation); + int depth = RandomUtil.gaussianAsPositiveInt(random, average, stdDeviation); StringBuffer buf = new StringBuffer(); for (int i = 0; i < depth; i++) { if (i != 0) { @@ -62,7 +63,7 @@ public static String randomId() { - int len = gaussianAsPositiveInt(AVERAGE_ID_LEN, AVERAGE_ID_DEV); + int len = RandomUtil.gaussianAsPositiveInt(random, AVERAGE_ID_LEN, AVERAGE_ID_DEV); StringBuffer buf = new StringBuffer(); for (int i = 0; i < len; i++) { int offset = random.nextInt(26); @@ -72,31 +73,6 @@ return buf.toString(); } - /** - * Approximate a gaussian distrib with only only positive integer values - * - * @param average - * @param stdDeviation - * @return - */ - public static int gaussianAsPositiveInt(int average, int stdDeviation) { - if (average < 1) { - throw new IllegalArgumentException( - "The average must not be smaller than 1."); - } - - if (stdDeviation < 1) { - throw new IllegalArgumentException( - "The stdDeviation must not be smaller than 1."); - } - - double d = random.nextGaussian() * stdDeviation + average; - int result = 1; - if (d > 1.0) { - result = (int) Math.round(d); - } - return result; - } /** * Returns 3 for root, 3 for children of root, 9 for offspring of generation 2 @@ -114,7 +90,7 @@ return 9; } else { if (shouldHaveChildrenWithProbabilitz(0.5)) { - return gaussianAsPositiveInt(AVERAGE_CHILDREN_COUNT, CHILDREN_COUNT_VAR); + return RandomUtil.gaussianAsPositiveInt(random, AVERAGE_CHILDREN_COUNT, CHILDREN_COUNT_VAR); } else { return 0; } Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusMakerUtil.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/CorpusMakerUtil.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,156 @@ +/** + * Logback: the generic, reliable, fast and flexible logging framework. + * + * Copyright (C) 2000-2009, QOS.ch + * + * This library is free software, you can redistribute it and/or modify it under + * the terms of the GNU Lesser General Public License as published by the Free + * Software Foundation. + */ +package ch.qos.logback.classic.corpus; + +import java.util.List; +import java.util.Random; + +import ch.qos.logback.classic.Level; + +public class CorpusMakerUtil { + + // level distribution is determined by the following table + // it corresponds to TRACE 20%, DEBUG 30%, INFO 30%, WARN 10%, + // ERROR 10%. See also getRandomLevel() method. + static final double[] LEVEL_DISTRIBUTION = new double[] { .2, .5, .8, .9 }; + + // messages will have no arguments 90% of the time, one argument in 3%, two + // arguments in 3% and three arguments in 3% of cases + static final double[] ARGUMENT_DISTRIBUTION = new double[] { .90, .933, 0.966 }; + + static final double THROWABLE_PROPABILITY_FOR_WARNING = .1; + static final double THROWABLE_PROPABILITY_FOR_ERRORS = .3; + static final double NESTING_PROBABILITY = .5; + + static final int AVERAGE_LOGGER_NAME_PARTS = 6; + static final int STD_DEV_FOR_LOGGER_NAME_PARTS = 3; + + static final int AVERAGE_MESSAGE_WORDS = 8; + static final int STD_DEV_FOR_MESSAGE_WORDS = 4; + + final Random random; + List<String> worldList; + + CorpusMakerUtil(long seed, List<String> worldList) { + random = new Random(seed); + this.worldList = worldList; + + } + + String getRandomWord() { + int size = worldList.size(); + int randomIndex = random.nextInt(size); + return worldList.get(randomIndex); + } + + int[] getRandomAnchorPositions(int wordCount, int numAnchors) { + // note that the same position may appear multiple times in + // positionsIndex, but without serious consequences + int[] positionsIndex = new int[numAnchors]; + for (int i = 0; i < numAnchors; i++) { + positionsIndex[i] = random.nextInt(wordCount); + } + return positionsIndex; + } + + private String[] getRandomWords(int n) { + String[] wordArray = new String[n]; + for (int i = 0; i < n; i++) { + wordArray[i] = getRandomWord(); + } + return wordArray; + } + + MessageEntry getRandomMessageEntry() { + int numOfArguments = getNumberOfMessageArguments(); + Object[] argumentArray = null; + if (numOfArguments > 0) { + argumentArray = new Object[numOfArguments]; + for (int i = 0; i < numOfArguments; i++) { + argumentArray[i] = new Long(random.nextLong()); + } + } + int wordCount = RandomUtil.gaussianAsPositiveInt(random, + AVERAGE_MESSAGE_WORDS, STD_DEV_FOR_MESSAGE_WORDS); + String[] wordArray = getRandomWords(wordCount); + + int[] anchorPositions = getRandomAnchorPositions(wordCount, numOfArguments); + for (int anchorIndex : anchorPositions) { + wordArray[anchorIndex] = "{}"; + } + + StringBuilder sb = new StringBuilder(); + for (int i = 1; i < wordCount; i++) { + sb.append(getRandomWord()).append(' '); + } + sb.append(getRandomWord()); + + return new MessageEntry(sb.toString(), argumentArray); + } + + Throwable buildThrowable(double i) { + return null; + } + + Throwable getRandomThrowable(Level level) { + double rn = random.nextDouble(); + if ((level == Level.WARN && rn < THROWABLE_PROPABILITY_FOR_WARNING) + || (level == Level.ERROR && rn < THROWABLE_PROPABILITY_FOR_ERRORS)) { + return ExceptionBuilder.build(random, NESTING_PROBABILITY); + } else { + return null; + } + } + + int getNumberOfMessageArguments() { + double rn = random.nextDouble(); + if (rn < ARGUMENT_DISTRIBUTION[0]) { + return 0; + } + if (rn < ARGUMENT_DISTRIBUTION[1]) { + return 1; + } + if (rn < ARGUMENT_DISTRIBUTION[2]) { + return 2; + } + return 3; + } + + String getRandomLoggerName() { + int parts = RandomUtil.gaussianAsPositiveInt(random, + AVERAGE_LOGGER_NAME_PARTS, STD_DEV_FOR_LOGGER_NAME_PARTS); + StringBuilder sb = new StringBuilder(); + for (int i = 1; i < parts; i++) { + sb.append(getRandomWord()).append('.'); + } + sb.append(getRandomWord()); + return sb.toString(); + } + + Level getRandomLevel() { + double rn = random.nextDouble(); + if (rn < LEVEL_DISTRIBUTION[0]) { + return Level.TRACE; + } + if (rn < LEVEL_DISTRIBUTION[1]) { + return Level.DEBUG; + } + + if (rn < LEVEL_DISTRIBUTION[2]) { + return Level.INFO; + } + + if (rn < LEVEL_DISTRIBUTION[3]) { + return Level.WARN; + } + + return Level.ERROR; + } +} Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,33 @@ +package ch.qos.logback.classic.corpus; + +import java.io.IOException; +import java.util.Random; + +public class ExceptionBuilder { + + static Throwable build(Random r, double nestingProbability) { + double rn = r.nextDouble(); + boolean nested = false; + if (rn < nestingProbability) { + nested = true; + } + + Throwable cause = null; + if(nested) { + cause = makeThrowable(r, null); + } + return makeThrowable(r, cause); + } + + private static Throwable makeThrowable(Random r, Throwable cause) { + int exType = r.nextInt(4); + switch(exType) { + case 0: return new IllegalArgumentException("an illegal argument was passed", cause); + case 1: return new Exception("this is a test", cause); + case 2: return new IOException("an io error occured", cause); + case 3: return new OutOfMemoryError("ran out of memory"); + } + return null; + } + +} Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/MessageEntry.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/MessageEntry.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,27 @@ +package ch.qos.logback.classic.corpus; + +public class MessageEntry { + + + final String message; + final Object[] argumentArray; + + public MessageEntry(String message) { + this(message, null); + } + + + public MessageEntry(String message, Object[] argumentArray) { + this.message = message; + this.argumentArray = argumentArray; + } + + public String getMessage() { + return message; + } + + public Object[] getArgumentArray() { + return argumentArray; + } + +} Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/RandomUtil.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/RandomUtil.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,42 @@ +/** + * Logback: the generic, reliable, fast and flexible logging framework. + * + * Copyright (C) 2000-2009, QOS.ch + * + * This library is free software, you can redistribute it and/or modify it under + * the terms of the GNU Lesser General Public License as published by the Free + * Software Foundation. + */ +package ch.qos.logback.classic.corpus; + +import java.util.Random; + +public class RandomUtil { + + + /** + * Approximate a gaussian distrib with only positive integer values + * + * @param average + * @param stdDeviation + * @return + */ + static public int gaussianAsPositiveInt(Random random, int average, int stdDeviation) { + if (average < 1) { + throw new IllegalArgumentException( + "The average must not be smaller than 1."); + } + + if (stdDeviation < 1) { + throw new IllegalArgumentException( + "The stdDeviation must not be smaller than 1."); + } + + double d = random.nextGaussian() * stdDeviation + average; + int result = 1; + if (d > 1.0) { + result = (int) Math.round(d); + } + return result; + } +} Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/TextFileUtil.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/TextFileUtil.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,34 @@ +package ch.qos.logback.classic.corpus; + +import java.io.BufferedReader; +import java.io.IOException; +import java.util.ArrayList; +import java.util.List; + +public class TextFileUtil { + + //FileReader fr = new FileReader(filename); + //BufferedReader br = new BufferedReader(fr); + + public static List<String> toWords(BufferedReader br) throws IOException { + + + // (\\d+)$ + //String regExp = "^(\\d+) "+ msg + " ([\\dabcdef-]+)$"; + //Pattern p = Pattern.compile(regExp); + String line; + + List<String> wordList = new ArrayList<String>(); + + while ((line = br.readLine()) != null) { + //line = line.replaceAll("\\p{Punct}+", " "); + String[] words = line.split("\\s"); + for(String word: words) { + wordList.add(word); + } + } + br.close(); + + return wordList; + } +} Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/FileToWord.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/FileToWord.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,32 @@ +package ch.qos.logback.classic.corpusTest; + +import static org.junit.Assert.*; + +import java.io.BufferedReader; +import java.io.IOException; +import java.io.StringReader; +import java.util.List; + +import org.junit.Test; + +import ch.qos.logback.classic.corpus.TextFileUtil; + +public class FileToWord { + + @Test + public void smoke() throws IOException { + String s = "When on board H.M.S. 'Beagle,' as naturalist, I was much struck with\r\n" + + "certain facts in the distribution of the inhabitants of South America,\r\n" + + "and in the geological relations of the present to the past inhabitants\r\n" + + "of that continent."; + + StringReader sr = new StringReader(s); + BufferedReader br = new BufferedReader(sr); + List<String> wordList = TextFileUtil.toWords(br); + assertEquals(38, wordList.size()); + assertEquals("When", wordList.get(0)); + assertEquals("'Beagle,'", wordList.get(4)); + assertEquals("of", wordList.get(17)); + + } +} Added: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/RandomUtilTest.java ============================================================================== --- (empty file) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpusTest/RandomUtilTest.java Wed Mar 4 21:05:53 2009 @@ -0,0 +1,43 @@ +package ch.qos.logback.classic.corpusTest; + +import static org.junit.Assert.assertEquals; + +import java.util.Random; + +import org.junit.Test; + +import ch.qos.logback.classic.corpus.RandomUtil; + + +public class RandomUtilTest { + + + @Test + public void smoke() { + + int EXPECTED_AVERAGE = 6; + int EXPECTED_STD_DEVIATION = 3; + + long now = System.currentTimeMillis(); + Random r = new Random(now); + int len = 3000; + int[] valArray = new int[len]; + for(int i = 0; i < len; i++) { + valArray[i] = RandomUtil.gaussianAsPositiveInt(r, EXPECTED_AVERAGE, EXPECTED_STD_DEVIATION); + } + double avg = average(valArray); + for(int x: valArray) { + System.out.println(""+x); + } + assertEquals(EXPECTED_AVERAGE, avg, 0.1); + } + + public double average(int[] va) { + double avg = 0; + for(int i = 0; i < va.length; i++) { + avg = (avg*i+va[i])/(i+1); + } + return avg; + } + +}

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svn commit: r2197 - logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus
by noreply.ceki＠qos.ch 09 Mar '09

09 Mar '09

Author: ceki Date: Mon Mar 9 11:43:41 2009 New Revision: 2197 Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java Log: make the code compile with JDK 1.5 Modified: logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java ============================================================================== --- logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java (original) +++ logback/trunk/logback-classic/src/test/java/ch/qos/logback/classic/corpus/ExceptionBuilder.java Mon Mar 9 11:43:41 2009 @@ -9,9 +9,10 @@ */ package ch.qos.logback.classic.corpus; -import java.io.IOException; import java.util.Random; +import javax.management.remote.JMXProviderException; + public class ExceptionBuilder { static Throwable build(Random r, double nestingProbability) { @@ -33,7 +34,7 @@ switch(exType) { case 0: return new IllegalArgumentException("an illegal argument was passed", cause); case 1: return new Exception("this is a test", cause); - case 2: return new IOException("an io error occured", cause); + case 2: return new JMXProviderException("jmx provider exception error occured", cause); case 3: return new OutOfMemoryError("ran out of memory"); } return null;

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