EFFECTS OF AMPHIMIXIS ON THE GERM-PLASM 235 



CHAPTER VIII 



MODIFICATIONS OF THE GERM-PLASM CAUSED BY 



AMPHIMIXIS 



I. The Necessity of a Halving of the Germ-Plasm 



By the process of amphimixis the hereditary substances of two 

 individuals become united into one substance in the offspring. 

 If the process is repeated in every generation, a doubHng of 

 these individually different hereditary substances must take place 

 each time, and the mass of germ-plasm and the number of idants 

 must likewise be doubled. As a matter of fact this cannot and 

 does not occur, for in every species the number of idants remains 

 the same throughout all generations. The unlimited increase 

 of the germ-plasm must therefore be prevented in some way or 

 other. 



The mass of germ-plasm might possibly remain constant if 

 its growth stopped in the young germ-cells when only half the 

 normal quantity had been formed. It is quite conceivable that 

 a continual increase in mass might in this way be prevented, if, 

 contrary to the theory of the germ-plasm here propounded, we 

 were to imagine that the idioplasm merely consists of ultimate 

 vital particles — 'pangenes,' 'primary constituents,' or whatever 

 else we choose to call them — which are not combined into units 

 of a higher order. 



If, however, we assume the existence of a germ-plasm in the 

 sense in which I use the word, — /.<?., an idioplasm in which the 

 ultimate bearers of vitality (biophors) are combined to form 

 units of a higher order, the determinants and ids, having a 

 definite structure and size, — it is evident that the amount of 

 germ-plasm would not remain constant, or at most it would only 

 remain so for a few generations, as long, that is, as each kind of 

 germ-plasm is represented by several ids. As soon as this stage 

 was reached, a decrease in growth could no longer prevent a 

 doubHng of the mass ; this could, in fact, only be prevented by 

 the removal of half of the nuniber of ids present in the cell. 



