OBSERVATIONS AND EXPERIMENTS 229 



of being influenced by any modification produced in 

 specialised parts of the organism and also the hered- 

 itary transmission of acquired characters. If we 

 analyse it closely, however, we shall see that it is 

 neither as deep nor as important as we might think. 



Ontogenetic differentiation results from the pre- 

 dominance of certain substances in the various cells. 

 Some of those substances arise de novo in those cells, 

 others come from the ovum in which they originate. 

 The ovum, like every other cell, possesses a certain 

 contractility, a certain excitability, which, whenever a 

 muscle or nerve cell becomes differentiated, develops 

 considerably in those cells at the expense of other 

 properties. If we admit that contractility and ex- 

 citability are due to a certain substance or to a special 

 structural disposition, it follows that this substance 

 or this disposition must also exist in the ovum which 

 possesses such properties in a lesser degree. 



The same may be true of some other less salient 

 characters, although we cannot say that it is true of 

 all characters, for we would then return to the absurd 

 idea of representative particles with all its complica- 

 tions and its improbability. 



Those substances, however, do not represent the 

 various functions of the organism, nor do they remain 

 in the ovum in prevision of an ulterior development; 

 they are merely substances necessary to the existence 

 and the proper functioning of the ovum. 





