History of the Theory of Heredity. 37 



process I propose to designate by a, single word — Peri- 

 genesis, the periodic wave-generation of the organic 

 molecules or plastidules. 



"This mechanical hypothesis is a true explanation of 

 the process of organic development. . . . 



'*The designation of this branched wave-motion of 

 the plastidule by the word perigenesis or tvave genera- 

 tion serves to emphasize the distinctive characteristic 

 which separates this branched motion from all similar 

 periodic phenomena. This peculiarity depends upon 

 the reproductive power of the plastidule, and this again 

 is brought about by its peculiar atomic composition. 

 This power of reproduction which alone renders possible 

 the multiplication of the plastids is, however, the equiv- 

 alent of the memory (Gediichtness) of the plastidule. 



"This brings us to Ewald Hering's ably established 

 yiew that unconscious memory is the most important 

 characteristic of organized matter, or more properly of 

 the organizing plastidules. Memory is the chief factor 

 in the process of development of organisms. Through 

 the memory of the plastidules the plasson has the power 

 to carry over from generation to generation by inheri- 

 tance, in continuous periodic motion, its characteristic 

 peculiarities, and to add to these the new experiences 

 which the plastidules have acquired through adaptation 

 in the course of their evolution. 



"I have shown that each organic form is the neces- 

 sary product of two mechanical factors — an inner factor, 

 heredity, and an outer factor, variability, or a power of 

 adaptation. 



" By the hypothesis of perigenesis we are able to more 

 sharply define these two fundamental laws of the modi- 

 fication of organisms, for heredity is the memory of the 

 plastidules: variahility their power of perception (Die 



