192 ORGANIC EVOLUTION CONSIDERED 



other cases; and it implies that the female progen- 

 itors of the existing spur-bearing species were once 

 encumbered with an injurious appendage." * 



In this he admits that the rudimentary spurs of 

 female birds have never been functional, and, conse- 

 quently, they cannot come under that law which it is 

 claimed gives meaning to their existence. 



The greatest difficulty in this matter is to account 

 for the evolution of functional spurs in either sex — and 

 their being in the best positions only increases the 

 difficulty. 



Other rudimentary organs furnish difficulties which, 

 I think, the theory of evolution fails to meet. For 

 example, foetal calves have rudimentary incisor teeth 

 in the upper jaw which never cut the gums, and these, 

 it is claimed, indicate the presence, in their stead, of 

 functional teeth in distant ancestors. 



If the ruminants at one time had upper incisors 

 that were functional, I do not see how they could 

 have ceased to perform their work and have disap- 

 peared. It could, so far as I can see, be no conceiv- 

 able advantage to a ruminant to lose its upper incis- 

 ors. With these teeth present, they could nip the 

 grass more closely, and thus the better obtain a supply 

 of food in time of scarcity. Besides, they might 

 serve, as in the case of the horse, as a means of de- 

 fense. The upper incisors could not have disap- 

 peared because they were useless nor because they 

 were not used, for they were of constant service. 

 Natural selection cannot, therefore, account for their 

 disappearance. 



These teeth must have passed into the rudimentary 



condition in the primitive ruminant stock before it 



had subdivided, for this is indicated by their general 



absence among living ruminants. If this is true, they 



* Descent, Vol. 2, p. 155. 



