344 SAMl'EI. W'TLKK AND MEMORY THEORIES 



hypothesis set up is that every functional stimulus is trans- 

 formed into specific vital energy, and deposits in the nucleus 

 of the cell a specific substance which is capable of discharging, 

 in an inverse direction, the nervous current which has formed 

 it, as soon as the dynamical equilibrium of the organism 

 is restored to the state in which it was when the original 

 stimulus acted upon it. These specific nuclear substances, 

 different for each cell, are accumulated also in the nuclei of 

 the germinal substance, constituting what Rignano calls the 

 central zone of development. That is to say, each functional 

 adaptation changes slightly the dynamical equilibrium of the 

 organism, and this change in the system of distribution of 

 the nervous currents leads to the deposit in the central zone 

 of development of a new specific substance. In the develop- 

 ment of the next individual this new specific element enters 

 into activity, and reproduces the nervous current which has 

 formed it, as soon as the organism reaches the same con- 

 ditions of dynamical equilibrium as those obtaining when 

 the stimulus acted on the parent. 



Development can thus be regarded as consisting of a 

 number of stages, at each of which new specific elements 

 enter automatically into play and lead the embryo from that 

 stage to the stage succeeding. The germinal substance on 

 this theory of Rignano's is to be regarded as being composed 

 of a large number of specific elements, originally formed as 

 a result of each new functional adaptation, but now forming 

 part of the hereditary equipment. 



The theory represents an advance upon the more static 

 conceptions of Semon. It owes much to Roux's influence. 



In this country, the mnemic theories have been championed 

 particularly by M. Hartog l and Sir Francis Darwin. - 



Sec /'/-(>/>/ a/is of Life and Reproduction, London, 1913. 

 - 1' residential Address to the British Association, 1908. 



