J 



SIVATHERIUM AND GIRAFFE. 117 



very little further, to come to the lines of succes- 

 sive forms or stirpes, which my h^-pothesis suggests. 

 This view becomes the more striking when we re- 

 member that any variations which we now see, 

 take place within a space of time extremely small 

 in comparison with those which geologj- allows for 

 its phenomena. " Although," says Mr. Halde- 

 man, " we may not be able, artificially, to produce 

 a change beyond a definite point, it would be a 

 hasty inference to suppose that a physical agent 

 acting gradually for ages, could not carry the varia 

 tion a step or two further." 



I may here advert to a fallacy which has been 

 one of the principal difficulties in the way of the 

 supposition of every kind of transmutation. It is 

 always taken for granted that the parental animal 

 must be extinguished in consequence of the 

 change. Thus we find a suggestion by M. St. 

 Hilaire that the modem girafie may be a modifi- 

 cation of the sivatherimn of the Indian tertiaries, 

 met very complacently by a reference to the dis- 

 covery of Dr. Falconer, that, in these tertiaries, 

 the giraffe is associated with the sivatherimn. 

 So, also, the suggestion that the hare of Siberia, 

 with its curtailed ears, shorter hind legs, and ab- 

 sence of tail, may be a modification of the ordinary 



