356 eepoet— 1879. 



Buffon, in his chapter on the animals of the Old and New World, remarks, 1 * It 

 is not impossible that the whole 2 of the New World's animals are derived from the 

 same source as those of the old, whence they have descended.' . . . . ' Nature is 

 in a state of perpetual flux.' In his chapter on the Degeneration of Animals 3 he 

 sums up saying, ' After comparing all the animals, and arranging them each in 

 their own group, we shall find that the two hundred kinds described here may be 

 reduced to a small number of original forms, whence it may be all the rest have 

 issued.' 



As to the modes and causes of the origin of new forms, he entertained four 

 connected opinions : 



(1) He attributed much modifying efficacy to migrations ; 



(2) Also to the direct action of external conditions ; 



(3) He believed largely in the origin of new forms by degradation ; and 



(4) He regarded each animal as the manifestation of an individuating force,, 

 lying, as it were, at the root of the changes manifested by it. 



The view that migration (with isolation) is a necessary antecedent to the origin 

 of new species is one which has been advocated by a modern naturalist, Moritz 

 Wagner; 4 who does not hesitate to affirm 5 that the formation of a really new 

 species ' will only succeed when a few individuals, having crossed the barriers of 

 their station, are able to separate themselves for a long time from the old stock.' 



In support of his view the author brings forward a multitude of interesting 

 facts, one of the most significant of which appears to me to be the following. It 

 concerns Beetles of Tropical America of the genus Tetracha. In Venezuela (as also 

 in the western part of Central America) , he tells us, rivers flow partly through 

 savannahs, where they have undermined the light tufaceous soil, forming deep beds 

 with high precipitous banks. According to Professor Wagner, individual beetles 

 from the highlands have thus been isolated, and in no longer time than has been 

 required by the rivers to undermine the loose soil of the savannah, have given rise 

 to a distinct species markedly different in form and colour. It is to similar causes — 

 migration and complete isolation — that he traces the formation of distinct races of 

 men : a formation he deems no longer possible, while the wide diffusion of mankind 

 renders more and more difficult the evolution of new species of animals of any kind. 



Instances which appear to support this view will readily suggest themselves to- 

 the naturalist — instances, that is, of forms which are both pecidiar in structure and 

 remote and isolated as to their habitat. 6 Thus for example, even in the group which 

 structurally most resembles us, we have the Orang confined to very limited tracts 

 in Borneo and Sumatra, and the Gorilla to a small portion of Western Africa. 

 The Proboscis Monkey is found nowhere but in Borneo, while the singular ape 

 named 'Roxellana' (from its wonderfully 'tip-tilted' nose) is confined to the 

 lofty and isolated mountains of Moupin in Thibet. The very peculiar black ape 

 (Cynopithecus) is limited to Celebes and Batchian, while the Baboon, which has 

 the baboon character of muzzle most developed, was found at the extreme south of 

 the African continent. 



1 Op. cit. vol. ix. p. 127. 



2 He thought, that the American Jaguars, Ocelots, &c, and even the Peccary, 

 were positive degradations of Old World forms. He thought that the Llama, the 

 American Apes, Agoutis, and Ant-eaters might be examples of such forms ; but the 

 Opossum, Sloths and Tapirs he took to be original species. (See vol. xiv. 

 up. 272, 273.) 



3 Vol. xiv. p. 358. 



4 In a paper read before the Koyal Academy of Sciences at Munich on March 2, 

 1868. This has been translated by Mr. James L. Laird, and published by Edward 

 Stanford in 1873. 



5 Op. cit. p. 29. 



6 Isolation, it ought to be remembered, may take place as the result not only of 

 changes in inorganic nature (such as the formation of islands, and the excavation of 

 river beds), but also by the presence of enemies in intermediate tracts, by the cir- 

 cumstance that the food of the species is found only in certain restricted localities, 

 and by whatever other causes determine the extinction of a species in a given place. 





