17 DARWINISM TO-DAY. 



for modification in the most manifold ways, in which the 

 first stages are often of immediate use." 



Following these suggestions as to the aid that selection 

 may have from various helping conditions to make its 

 starts, Plate discusses as further similarly help- 

 aid fronAn- 1 ^ conditions or auxiliary principles three most 



herited results important matters, namely, the effects of con- 



of use, from or- . , t . . , . , 



thogenesis and tinued use on parts, the principle of orthogen- 

 discontinuons es j s> anc j ^ ie f ac t s of sudden discontinuous 



variation. 



variation. But as these three categories of 

 biological phenomena and principles are exactly those, 

 among others, which anti-Darwinians hold to be not aids 

 to the selection theories, but to be the basis if not of actually 

 replacing or substitutionary theories, at least of precisely 

 those objections to the species-forming capacity of the strict 

 Darwinian factors which have necessitated some of the 

 principal concessions made by the Darwinists, it is obvious 

 that Plate's discussion of them is in itself simply the actual 

 making of the concessions already noted as having been 

 admitted by most Darwinians. Each of these categories 

 of phenomena and principles is of course of much import- 

 ance and interest, and they will all be found to be fairly fully 

 set out in the chapters following this one. 



Plate's answers to the second important objection, namely, 

 that selection relies too much on chance and is therefore 



improbable and inexact, may now be noted. He 



Answers to 



the objection distinguishes two phases of this objection. The 



concerning the first he expresses as follows: "It is highly im- 

 dependence of 



selection on probable that for the progressive development 

 or perfecting of an organ there will always 

 appear just at the needed time the variation necessary for 

 selection, that is, the exactly needed adaptive modification." 

 The second phase is : "It is highly improbable that in the 

 development of a complicated organ, or body-part, or in 

 the perfecting of a changing adaptation the numerous indis- 



