Litei'avy Notices. 11 



the same author in which he has discussed the trutli of this postulate. ^ 

 The two books should be read together, if one would gain a true view 

 of Mr. Romanes' views on these important questions. c. j. h. 



Germinal Selection. ^ 



The address delivered by Dr. Weismann before the International 

 Congress of Zoologists at Leyden, i6 Sept., 1895, is here expanded 

 and translated. The fundamental difficulty urged against Weismann and 

 the other so-called neo-Darwinists by their critics is the impossibility of 

 accounting for many of the adaptations as we find them on the basis of 

 a theory of natural selection which recognizes only indefinite variabil- 

 ity. The simultaneous occurrence of the variations necessary to pro- 

 duce, e. g., a case of mimicry in a butterfly, is hardly credible except 

 on some hypothesis of definitely directed variability. The hypothesis 

 of germinal selection assumes that when natural selection acting on 

 accidental somatic variations in the manner usually described has re- 

 sulted in a slight increase in the efficiency of the part in the given di- 

 rection, then the determinants corresponding to that part in the germ- 

 plasm of the next generation will be more vigorous than the determi- 

 nants of other parts and in the struggle for food will outstrip them. 

 Thus that part will in the adult be stronger than it was in the previous 

 generation, and this result will be cumulative. So the germ is progress- 

 ively modified in the direction set by utility. 



Though very little has yet been published on this specific phase of 

 the problem, the general question of definitely directed variation is one 

 to which every thoughtful biologist must have given some attention. 

 The success of this attempt to explain the mechanism of the process 

 will rest on the value of Dr. Weismann's scheme of the hereditary ma- 

 chinery. And in estimating this we must recognize the purely symboHc 

 nature of the conceptions used by the author of this scheme, a fact 

 of which, as he points out, his critics have often failed to take account. 



To one who, like the reviewer, is unwilling to admit the absolute 

 non-transmissibility of somatic characters it is obvious that the argu- 

 ment for germinal selection cannot be accepted exactly as here out- 

 hned ; yet the principle may be a true one and is not necessarily incom- 

 patible with an application of some form of the Lamarkian doctrine as 

 well. c. J. H. 



1 Darwin and After Darwin. II. Post-Darwinian Questions, Heredity and 

 Utility. Chicago, The Open Court Publishing Co., 1895. 



- Weismann, August. On Germinal Selection. Chicago, The Open Court 

 Publishing Co., 1896. Price 25 cents. 



