Internal Factors of Sex Determination 417 



tion. In the case of the unfertilized egg of the bee it has been 

 shown by Petrunkewitsch that the half (reduced) number of 

 chromosomes is left in the egg. He states that there occurs a 

 doubling of the number of chromosomes before the first seg- 

 mentation nucleus is formed, so that the full number is restored. 

 This result is not in harmony with Meves's study of the sperma- 

 togenesis, and as Giglio-Tos has pointed out the whole question is 

 in such a confused state that we must await further observations. 



Injiuence of the Cytoplasm 



Most modern theories of sex determination have been based 

 on changes in the nucleus rather than in the cytoplasm. Yet 

 since the differentiation of the cell takes place in the cytoplasm, 

 it may seem that the initial differences might be traced to that 

 part ; but owing to the fact that the different parts of the un- 

 differentiated cytoplasm show little differences in staining capaci- 

 ties, it has not been possible to gather many facts that can be 

 utihzed in the formation of a cytoplasm theory. One considera- 

 tion above all others has, I think, led modern cytologists to re- 

 gard the nucleus rather than the cytoplasm as the initiator in the 

 formation of the characters of the embryo. It has become an 

 unchallenged or seldom questioned dictum that the nucleus 

 must transmit the qualities of the germ-cells, because the quali- 

 ties of the father are brought into the egg by the spermatozoon, 

 and it is assumed that the nucleus of the spermatozoon is the 

 only part of it that contributes anything worth considering to 

 the fertihzed egg. Furthermore, since the nucleus of the sperma- 

 tozoon consists of almost solid chromatin, it has been inferred 

 that the chromosomes alone carry the hereditary qualities of 

 the germ-cells. But a consideration of all the facts will show, 

 I think, that there is at least a possibiHty that the protoplasm of 

 the sperm-cell may have something to do with the transmission 

 of the hereditary qualities of the father. If we trace the history 

 of the spermatozoon, we find that at no stage is all of the cyto- 

 plasm of the germ-cell from which it arises totally eliminated from 

 the cell. It is true that a part of the cytoplasm — it maybe a large 



