ri22 l\ CUMEliKNCK I.NÏKIIN A I l(i\ AI.K lil': CK.NKÏIUIK. 



loss ol' ri-rUlily and Ihc liUc, do iii>l api»';)!' nrdil al'lcr tlie Iwcnliclli f,a-ncralion 

 in inbrod rais. Accordin^ lo llic dirorlion in^^lli(•ll our |)crsoiial Lias leads ns. 

 wcwill cillior lay slress on Ihc facl llial drlnioi-alion occurs pvenliiallv . m- on 

 llic i'acl liial il does nol occur uniil aflci- Ihc Iwciiliclh g-encration. lînl apail 

 l'roin Personal bias, Ihe facl is provcd Ihal a pair ol" rats, given spacc. l'ouil 

 and aljsence from enemies \\ould grow inio vciy niany millions. (Bcroïc lin- 

 Iwcnlielh f>pncralion was rcachcd.) Wonld llie resniling mass as a wliolclhcn 

 fccl Ihc liarmlul efTccIs ofinbrceding? Wonld il lie slill practisinfi: indjrccdini;-. 

 W'hat is " inbrecding " wc inay now asU. AI ail cvcnis niany ni' Ihc lals in Ihc 

 Iwenlielh gencralion woidd lie dislanllx iclalcd lo onc anolhcr. Siiicc nian\ 

 animais will nol breed in caplivily. or as Ihe facl niay lie expresscd in olher 

 words, lose ail Iheir i'erlilily al once iindcr Ihis condition, il is nol snrprising 

 tliat loss of fertilily shonld sooncr or laler appear in captive stock, Uept on one 

 spot and prcventcd from exercising- ils own inslincts in many respects. But 

 the case, I believe, is quite olherwise in free slock whicli is sprcading rapidly 

 and filling np fresh space. 



Acknowleilgmcnt and ex/>l(ninlioit. — In arriving at niy conclusions, 1 hâve 

 received of course great help foin Ihe writings of olhers, whose works are well 

 know lo ail. Althoiigh itis for Ihe readerlo décide wbelher Ihis paper conlains 

 anything fresh and useful, yel I wish lo draw his attention lo the essential 

 point, — tliat the groups called species by Taxonomists are of ail sizes, 

 nnnierically, Ihat small groups such as I hâve called faniily groupsare picnlifnl 

 in nature, tbat if vve overlook them our descriptions of the animal kingdon w ill 

 bc inaccurate and our " explanations '' concerning it will be unnecessarilx ililli 

 cuit. I hâve used the old term " sporl "" inslead ol Ihe wortl — mulani, lo 

 indicalc Ihe abnormal fornis since Ihcy arc nol sUicliy comparable willi Ihc 

 typical mutants of Œnollicra, as dcscribcd by De Vries. 



The spécifie characterof a mulanl, aH'ccts the whole organism, it is somc- 

 thing whicb is Iransniitted invariably as a unit from parent lo oiïspring, it lias 

 no parts which can be manifesled separalely in dilTiTent individnals. The 

 groups, whicb I bave describcd, are varieties jndgcd from the viewpoini ol Ihe 

 Mutation Ihcory. It is I find difficull lo dislinguish between specic> and 

 varieties among Vertébrale animais. If Ihis dislinclionis proved. eventually. lo 

 hâve a nalural basis, tben \\c sliall liavc lo adniil Ihat mosl of our so called 

 species ai'c merely varieties. 



VARIATION PARIVII LES RATS DE L'INDE 



IIKSUMK 



La (Icsirnclion des rats dans II nilc. ordonnée poiu' condiallri> la propagation 

 de la peste, a été l'aile sur une très grande échelle depuis Itttl.'i cl l'anleur a été 

 à même d'examiner les peaux d'un grand nombre d'individus. 



Deux espèces siu'toul sont communes dans l'Inde : M)i< ititlii.<. espèce ré- 

 pandue dans le inontle entier, et Gunimnix brn(/i(!ciisls. ([u\ paT-aM élrc <onlinée 

 à l'Asie. 



Dans ti»«(////(/s, plusieurs rats noirs — coloris très rare dans celte espèce — 

 furent trouvés en un groupe. Ces individus avaient en commun d'autres carac- 



