294 NATURAL HISTORY. 



difficulties may disappear in the light of wider knowledge. 

 There are, however, certain general difficulties which 

 demand a moment's consideration, as indicating that 

 though we admit the action of ' natural selection ' to the 

 full, we must nevertheless look beyond and outside this 

 for the complete explanation of the existence and origin 

 of species. The general difficulties in question were per- 

 fectly recognised by Mr Darwin, and have been met by 

 him, as far as it is at present possible to meet them. The 

 principal are the following : * 



(i) One of the most general, and certainly one of the 

 most serious of the difficulties in the way of the theory of 

 natural selection is 'the uselessness of many organs in 

 their incipient stage.' Hosts of structures (such as the 

 milk-glands of the Quadrupeds, or the whalebone plates in 

 the mouth of the Whalebone Whales) are exceedingly 

 useful to the animal when perfectly developed; but it is 

 inconceivable that they could have benefited the animal 

 when first they began to be developed. According to the 

 theory of the evolution of species in general, and the 

 theory of natural selection in particular, milk-glands did 

 not exist in the animal forms out of which the class of the 

 Mammals was evolved, nor did baleen-plates exist in the 

 ancestors of the Whalebone Whales. There must, there- 

 fore, have been a time when milk-glands and baleen-plates 

 respectively first came into existence, and it is impossible 

 to suppose that they were suddenly produced in complete 

 structural and functional perfection as we now see them. 

 On the contrary, they must, to begin with, have been mere 



* An excellent resume of these objections is given by Mr Pascoe in his Notes on 

 Natural Selection and the Origin of Species, 1884. 



