RECENT LITERATURE. 119 



different theories of heredity, and finds them all unsatisfactory. 

 Some he rejects as altogether untenable, inasmuch as they do not 

 even profess to explain the inheritance of acquired characters. Chief 

 among these is Weismann's theory of the germ plasm, which our 

 author maintains does not even succeed in giving a rational explana- 

 tion of the law of recapitulation in ontogeny. Other theories, which 

 seem to be more in harmony with his own, he looks upon as being 

 much too vague and nebulous. 



Although the idea underlying it is simple enough, the mechanism 

 which the author suggests as an explanation of the inheritance of 

 acquired characters and of the repetition of the phylogenetic history 

 in the course of ontogeny is of so extremely complex a character, 

 and is based so much on the assumed behaviour of that form of 

 energy which he calls nervo-motive force, that it is by no means easy 

 to understand it or to decide how far theoretically it is workable and 

 sound. The idea is that a nervous current, like an electric current, 

 in passing through an accumulator can cause the deposit there of a 

 material substance — a potential element, which in its turn can give 

 rise to a current in the reverse direction corresponding to that which 

 caused its deposit. It is suggested that in the living organism the 

 nervous accumulators are situated in the nuclei of the cells. When 

 a functional stimulus is given, say by the use of some organ or in 

 response to the environment, the dynamic equilibrium is disturbed, 

 a nervous current flows, and in every nucleus through which it passes 

 there is deposited a potential element — in the germ cells as well as in 

 the somatic nuclei, although, so far as heredity is concerned, the latter 

 do not matter, since they are lost with the life of the individual. Up 

 to this point the analogy with electricity helps us to understand. 

 The electric accumulator is capable of giving off a current similar to 

 that which caused the deposit, and differing from it only in intensity. 

 But the nervous accumulator is no such simple affair. It must needs 

 be an accumulation of accumulators, each of which is capable of 

 giving rise to a current of a specific intensity corresponding to the 

 current which caused the deposit in it of the specific potential element. 

 To find out further how the machinery would work, our readers must 

 refer to the book itself, in which also they will find an abundance of 

 extracts from the writings of speculative philosophers, and an interest- 

 ing chapter on memory, w T hich is explained on the same lines as 

 ontogeny and the inheritance of acquired characters. It is to be 

 noted that the author, although a firm believer in the inheritance 

 of acquired characters, is candid enough to admit that no irrefutable 

 evidence has yet been brought forward to prove that acquired 

 characters are inherited. 



C. J. G. 



