II 8 EVOLUTION, OLD AND NEW. 



fortune of an ordinary man. I have spent many years 

 in experiments of this kind, and will give my results 

 when I come to my chapter on mules ; but I may as well 

 say at once that they have thrown but little light upon 

 the subject, and have been for the most part unsuc- 

 cessful." * 



" But these," he continues, " are the very points 

 which must determine our whole knowledge concerning 

 animals, their right division into species, and the true 

 understanding of their history." He proposes therefore, 

 in the present lack of knowledge, " to regard all ani- 

 mals as different species which do not breed together 

 under our eyes," and to leave time and experiment to 

 correct mistakes.f 



The Pig Doctrine of Final Causes. 



We have seen that the doctrine of the mutability 

 of species has been unfortunately entangled with that 

 of final causes, or the belief that every organ and every 

 part of each animal or plant has been designed to serve 

 some purpose useful to the animal, and this not only 

 useful at some past time, but useful now, and for all 

 time to come. He who believes species to be mutable 

 will see in many organs signs of the history of the 

 individual, but nothing more. Buffon, as I have said, is 

 explicit in his denial of final causes in the sense ex- 

 pressed above. After pointing out that the pig is an 

 animal whose relation to other animals it is difficult to 

 define, he says : 



"In a word, it is of a nature altogether equivocal 



* Tom. v. p. 63, 1755. f Ibid. p. 64. 



