FOUNDATION OP A THEORY OF HEREDITY. 215 



and that of the sperm-nucleus cannot be considered as male : both 

 are sexually indifferent. The last view has been recently formulated 

 by Strasburger, who holds that the quantity of the idioplasm 

 contained in the germ-nucleus must be reduced by one half, and 

 that a whole nucleus is again produced by conjugation with the 

 sperm-nucleus. Although I believe that 'the fundamental idea 

 underlying this hypothesis is perfectly correct, viz. that the in- 

 fluence of each nucleus is as largely dependent upon its quantity 

 as upon its quality, I must raise the objection that the decrease in 

 quantity is not the explanation of the expulsion of polar bodies. The 

 quantity of idioplasm contained in the germ-nucleus is, as a matter 

 of fact, not reduced by one-half but by three-fourths, for two 

 divisions take place one after the other. Thus by conjugation 

 with the sperm-nucleus, which we may assume to be of the same 

 size as the germ-nucleus, a nucleus is produced which can only 

 contain half as much idioplasm as was present in the original 

 germ-nucleus, before division. Strasburger's view leaves un- 

 explained the question why the size of the germ-nucleus, before the 

 expulsion of polar bodies, was thus twice as large ; and even if we 

 neglect the theory of ovogenetic nucleoplasm and assume that this 

 larger nucleus was entirely made up of germ-plasm, it must be 

 asked why the egg did not commence segmentation earlier. The 

 theory which explains the sperm-cell as the vitalizing principle 

 which starts embryonic development, like the spark which kindles 

 the gunpowder, would indeed answer this question in a very simple 

 manner. But Strasburger does not accept this theory, and holds, 

 as I do, a very different view, which will be explained later on. 



If, on the other hand, we assume that the germ-nucleus contains 

 two different kinds of nucleoplasm, the question is answered quite 

 satisfactorily. In treating of parthenogenesis, further on, I shall 

 mention a fact which seems to me to furnish a real proof of the 

 validity of this explanation ; and, if we accept this fact for the 

 present, it will be clear that the simple explanation now offered 

 of phenomena which are otherwise so difficult to understand, 

 would also largely support the theory of the continuity of the 

 germ-plasm. Such an explanation would, above all, very clearly 

 demonstrate the co-existence of two nucleoplasms with different 

 qualities in one and the same nucleus. My theory must stand 

 or fall with this explanation, for if the latter were disproved, the 



