( 511 ) 



Solomon Islands (!j, and so on, is no more miracnlous than the fact that there is 

 seasonal and local variation. 



Now, when we observe, for instance, that the Chinese P. ewypi/lus agrees best 

 with the Andaman form of that species, and that tlie Chinese P. antiphatrs comes 

 close to the (.'eylon form, while in both cases the representative inhabiting North 

 India, Burma, and Tenasserim is different, it would certainly sound preposterous to 

 explain the similarity in characters by assuming that there was at a former period 

 a land-connection between Ceylon, the Andaman Islands, and China independent of 

 Continental India. If we concede that this explanation cannot possibly be accepted, 

 and that consequently the similarity finds a correct explanation in the assumption 

 that it is merely the consequence of the similar eifect of the biological factors — the 

 effect is positive in respect to the characters which are modified, and negative in 

 respect to the characters which are not modified — of Ceylon, the Andamans, and 

 China, it is not difficult to perceive what great bearings the questions here discussed 

 have on the Geographical Distribution of Animals. Before proceeding to draw the 

 consequences, let us for a moment consider what is the aim of the study of the 

 Distribution of Animals. 



" If we keep in view . . . that the present distribution of animals upon the 

 several parts of the earth's surface is the final product of . . . the wonderful 

 revolutions in organic and inorganic nature," says Wallace,* ..." it will be 

 evident that the study of the distribution of animals and plants may add greatly to 

 our knowledge of the past history of our globe. It may reveal to us, in a manner 

 which no other evidence can, which are the oldest and most permanent features of 

 the earth's surface, and which the newest. It may indicate the existence of islands 

 or continents now sunk beneath the ocean, and which have left no record of their 

 existence save the animal and vegetable i)roductions which have migrated to 

 adjacent lands. It thus becomes an important adjunct to geology. . . . Our present 

 study may often enable us, not only to say where lands must have recently dis- 

 appeared, but also to form some judgment as to their extent, and the time that has 

 elapsed since their submersion." Indeed, the distribution of animals and plants, 

 especially if the extinct forms are also taken into account, illustrates wonderfully 

 the past history of the earth's surface, and the main object of the study of the dis- 

 tribution of animals and plants is to arrive at conclusions as to the probable past 

 changes in the geological features of the earth. This has so plainly been recognised 

 by nearly all recent systematists, as a glance in a volume of the Proceedings of 

 the Zoological Society or of the This will show, that, when dealing with a certain 

 group of animals from a certain locality, they endeavour to draw from the affinities 

 in tlie fauna of the respective district witli that of other districts conclusions 

 relating to tlie geological history of the locality, and it is very generally assumed 

 that similarity iu the components of the fauna of two areas means close 

 geological connection, while great dissimilarity means long geological separation. 

 So true this is in a great many cases, so erroneous is the generalisation. Nevertlie- 

 less it has very often been entirely lost sight of that the present distribution of 

 animals and jilants is, to use Wallace's words, " the final product of revolutions iu 

 inorganic and onjanic nature," and that accordingly the differences iu the fauna of 

 neighbouring districts and the similarities in the fauna of geographically widely 

 sejiarate areas can be quite indciiomlent of the geological history of the region iu 

 (juestion. If we now recall to mind what we have said above about the similarity 



* Piitrihution of AnimaU 187<*. ]>. 7. 



