FACTS 



241 



To give absolute value to the idea of species, it would 

 be necessary that the group called species should be separ- 

 ated from neighbouring groups by finite discontinuities ; 

 but it would also be necessary that there should exist 

 perfect continuity among the different individual types 

 constituting the species. 



Now this is not the case. 



We have seen how inevitable it is that finite differences 

 should exist between any two living individuals. It is the 

 existence of the step from any being whatever to every 

 other being. Accordingly, when there is a step from 

 one species to its neighbour, the discontinuity will differ 

 only in dimension from that which separates two individuals 

 of the same species. 



The definition of species becomes a question of apprecia- 

 tion it is no longer a strict and absolute definition. 



Before Transformism, belief in the possibility of an 

 absolute definition of species was possible and necessary. 

 The step separating individuals of the same species might 

 be passed over by the variations accompanying individual 

 multiplication ; but the discontinuities limiting species 

 were impassable. This was the basis of an absolute defini- 

 tion the variation resulting from adaptation and repro- 

 duction could not step over the limits of species. The species 

 had, therefore, to be defined after the fact, as a result of 

 prolonged observations. On the contrary, in the Trans- 

 formist theory we are obliged to define species a priori 

 for convenience in classification and without preoccupying 

 ourselves with metaphysics. 



I propose to define species the sum-total of individuals 

 among which only quantitative differences exist. Yet it is 

 easy to see that this would be simply conventional and 

 would even need other conventions, for we no longer believe 



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