34 DARWINISM TO-DAY. 



destroys the efficiency of its members in the struggle for life. 

 The question in many men's mouths to-day is, Why may not 

 variation be the actual determinant factor in species-forming, 

 in descent? It actually is, respond many biologists and 

 palaeontologists. 



Even Darwin believed such determinate variation to occur, 

 as is indicated by repeated statements in the "Origin of 

 Species." In chapter iv he says (to refer to but a single 

 one of these admissions) : "It should not, however, be over- 

 looked that certain rather strongly marked variations, which 

 no one would rank as mere individual differences, fre- 

 quently recur owing to a similar organisation being similarly 

 acted on of which fact numerous instances could be given 

 with our domestic productions. In such cases, if the vary- 

 ing individual did not actually transmit to its offspring its 

 newly acquired character, it would undoubtedly transmit to 

 them, as long as the existing conditions remain the same, 

 a still stronger tendency to vary in the same manner. There 

 can also be little doubt that the tendency to vary in the 

 same manner has often been so strong that all the individuals 

 of the same species have been similarly modified without the 

 aid of any form of selection. Or only a third, fifth, or 

 tenth part of the individuals may have been thus affected, of 

 which fact several instances could be given. Thus Graba 

 estimates that about one-fifth of the guillemots in the Faroe 

 Islands consist of a variety so well marked, that it was 

 formerly ranked as a distinct species under the name of 

 Uria lacrymans. In cases of this kind, if the variation were 

 of a beneficial nature, the original form would soon be sup- 

 planted by the modified form, through the survival of the 

 fittest." 



This problem of the existence or non-existence of deter- 

 minate variation is taken up in such detail in connection with 

 the explanation and discussion of various auxiliary or alter- 

 native theories of species-forming in later chapters of this 



