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. 
Influence oj 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 he 
utilized 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 spermatozoén, 
and it is assumed that the nucleus of the spermatozo6n is the 
only part of it that contributes anything worth considering to 
the fertilized egg. Furthermore, since the nucleus of the sperma- 
tozoén 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 possibility 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 spermatozoén, 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 may bea large 
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