DARWINISM DEFENDED. 135 



word selection in its name is fundamentally different from 

 natural selection in the Darwinian sense, and is indeed 

 an admission of the existence of variations maintained (not 

 by means of natural selection) along definite lines, result- 

 ing in a real orthogenesis. It attempts to offer a causo- 

 mechanical explanation of such un-Darwinian development. 

 By the theory of germinal selection, which is based abso- 

 lutely on the assumption that the plasm is composed of 

 biophors and determinants or at least of physical life units 

 of similar type and function, Weismann hopes to strengthen 

 four weak places in the general position of neo-Darwinism. 

 The theory explains (i) how in Panmixia (another Weis- 

 mannian contribution to neo-Darwinism, for account of 

 which see chapter viii) the degeneration of useless organs 

 is brought about, (2) how it is that for the continued 

 development of any certain complex adaptation exactly the 

 right variations shall appear at the needed time, (3) how co- 

 adaptation comes to exist, and finally (4) how variations 

 may come to be developed along fixed lines or in definite 

 directions without the aid of personal selection. Whether 

 the theory of germinal selection explains these four things 

 or not, what is to us for the moment the chief interest of the 

 theory is that it is put forward by Weismann, who is dis- 

 tinctly the foremost neo-Darwinian, to explain just these 

 things. For that makes of these things concessions that the 

 neo-Darwinians, the ultra-selectionists, feel forced to offer. 

 It should be noted, however, that perhaps Weismann does 

 not speak for all ultra-selectionists, for example, Lloyd 

 Morgan, Ray Lankester, and other English * Darwinians. 

 Certainly his theory of germinal selection is accepted by 

 few of them. 



On the whole, however, I think I speak perfectly fairly 

 in saying that the believers and defenders of the natural 

 selection theory to-day admit in large measure the valid- 

 ity of those criticisms which are directed at the inca- 



