An Exchange of Character-Units 243 



If every unit, that is, every inner character or every 

 material bearer of an external peculiarity, forms an en- 

 tity in each pronucleus, and if the two like units lie oppo- 

 site each other at any given moment, we may assume a 

 simple exchange of them. Not of all (for that would 

 only make the paternal pronucleus into a maternal one), 

 but of a larger, or even only a smaller part. How many 

 and which, may then simply be left to chance. In this 

 way all kinds of new combinations of paternal and mater- 

 nal units may occur in the two pronuclei, and when these 

 separate at the formation of the sexual cells, each of them 

 will harbor in part paternal, in part maternal units. These 

 combinations must be governed by the laws of proba- 

 bility, and from these, calculations may be derived, which 

 may lead to the explanation of the relations of affinity 

 between the children and their parents, the grandchildren 

 and their grand-parents. On the other hand a compari- 

 son of the results of this calculation and of direct obser- 

 vation will form the best, and for the time being, the only 

 possible means for a decision as to the correctness of our 

 supposition. 



The mutual influence of the two pronuclei shortly be- 

 fore their separation is therefore brought about, accord- 

 ing to our view, by an exchange of units. Every unit 

 can be exchanged only for a like one, which means for 

 one which, in the other pronucleus, represents the same 

 hereditary character. This rule appears to me to be un- 

 avoidable and reall}^ self-evident. For the children must 

 inherit all specific characters from their parents, and they 

 must also transmit all of them to their own progeny. 

 This exchange must hence be accomplished in such a way 

 that every pronucleus retains the entire series of units 

 of all the specific characters, and this result can evidently 



