The Zoologist — July, 1873. 3581 



A Difficulty for Darwinists. By Fkancis Hancock Balkwill. 



The third chapter of Mivart's 'Genesis of Species' states a 

 difficulty to the acceptance of Darwin's theory of the origin of 

 species thus : — " On this theory the chances are almost infinitely 

 great against the independent accidental occurrence and preserva- 

 tion of two similar series of minute variations resulting in the 

 independent development of two closely similar forms." Amongst 

 other illustrations of his theory, he mentions that Professor Huxley 

 had called his attention to the very striking resemblance between 

 certain teeth of the dog and the Thylacine. Having had this 

 difficulty very strongly forced upon my own mind in studying 

 mammalian teeth, I will try and state it more fully than is done by 

 Mivart. 



There are certain highly specialized and complicated organs 

 found upon diflferent animals, which are so similar that, upon 

 Darwin's theory, they ought to be hereditarily descended from or 

 related to each other; and yet, by the same theory, it seems 

 almost possible to prove that such could not be the case. Now if 

 this proof does hold good, some very considerable modifications of 

 the theory will be necessary. 



It is a fact familiar to every child that there are many kinds of 

 animals differing from one another in their general characters, and 

 that some of these animals are more alike than others, so that a 

 rough common sense classification soon takes place in the mind of 

 every individual, by which all the animals they are most familiar 

 with are probably arranged according to the peculiar conditions of 

 that individual. A settler in a new and wild country might have 

 two sub-kingdoms, viz. Wild and Domestic, of which the wild 

 might be divided thus: — 



Dangerous to human life ; 



Noxious, but not dangerous ; 



Injurious to crops; 



Useful for food ; 



Furnishing useful furs or skins ; 



and so forth. It would soon be observed that there were many 

 animals so similar in appearance that they might easily be mistaken 

 for each other, and that these similar animals had a similarity of 



SECOND SElilES — VOL. VIII. 2 I 



