INTRODUCTION 35 



Hereditary substances in the full meaning of the term — i.e., 

 that substance which contains all the primary constituents 

 of the whole organism, is merely the idioplasm of the germ- 

 cell, and it is advisable for practical purposes to denote 

 this first onto-idic stage by the short term gerr/i-plas>/i, which I 

 suggested for it at a time when the idea of idioplasm had not 

 been introduced. At that time I meant by the term 'germ- 

 plasm ' the hereditary substance of a germ-cell capable of 

 development, without expressing any opinion as to its position^ 

 or nature. We can now state that t/ie ger>ii-plas»i is tlie first 

 ontogenetic stage of the idioplasm of an animal or a plant, 

 whether the cell, in the nucleus of which it is contained, is 

 sexually differentiated or not. — 



We must next attempt to form an idea of the constitution and 

 nature of the germ-plasm, and of the ontogenetic stages of the 

 idioplasm, or onto-idic stages. 



I 



