230 Darwin, and after Darwin. 



entertained by any naturalist. Even though the 

 physiological distinction be allowed to count for 

 something in otherwise doubtful cases, no systematist 

 would constitute a species on such grounds alone. 

 Therefore we need not concern ourselves with this 

 definition, further than to observe that it is often 

 taken as more or less supplementary to each of the 

 following definitions. 



3. A group of individuals which, however many 

 characters they share with other individuals, agree in 

 presenting one or more characters of a peculiar kind, 

 with some certain degree of distinctness. 



In this we have the definition which is practically 

 followed by all naturalists at the present time. But, 

 as we shall presently see more fully, it is an extremely 

 lax definition. For it is impossible to determine, by 

 any fixed and general rule, what degree of distinctness 

 on the part of peculiar characters is to be taken as 

 a uniform standard of specific separation. So long 

 as naturalists believed in special creation, they could 

 feel that by following this definition (3) they were 

 at any rate doing their best to tabulate very real 

 distinctions in nature — viz. between types as originally 

 produced by a supernatural cause, and as subsequently 

 more or less modified (i. e. within the limits imposed 

 by the test of cross-fertility) by natural causes. But 

 evolutionists are unable to hold any belief in such 

 real distinctions, being confessedly aware that all 

 distinctions between species and varieties are purely 

 artificial. So to speak, they well know that it is 

 they themselves who create species, by determining 

 round what degrees of differentiation their diagnostic 

 boundaries shall be drawn. And, seeing that these 



