CLEAVAGE AND DIFFERENTIATION 



Thus finally every cell in the most complex organism 

 has in its nucleus all the potencies bound except that one 

 which is free in the cytoplasm and which makes the cell 

 specific. The egg-cell, for example, the moment it becomes 

 differentiated from other cells of the body is such because 

 it has in its nucleus all bound potencies except that which 

 makes it an egg-cell. And it is this potency in the cyto- 

 plasm which determines the future growth and differentia- 

 tion of the egg to that moment, when these bound potencies 

 are thrown again into the cytoplasm. The sperm-cell is 

 such because in its nucleus are all the potencies bound except 

 that which determines the sperm-character of the cell. 

 This potency determines the further differentiation of the 

 spermatozoon and most probably is responsible for the 

 nullification of the potencies in the sperm-nucleus. 



This conception of mine concerning the action of the gene 

 offers a far better interpretation for several phenomena 

 than the hitherto proffered conceptions. Thus, for exam- 

 ple, can we state that sex-differentiation is resident in the 

 cytoplasm. For the majority of animals, the taking out 

 from the cytoplasm of more sexual potencies by the chro- 

 mosomes results in femaleness. So in those experimental 

 conditions, where more than one set of chromosomes is 

 present, the organism becomes female. The taking out of 

 fewer sex-potencies by the chromosomes gives rise to a 

 male. Thus an egg with half the somatic number of chro- 

 mosomes, the so-called haploid number, is always, so far 

 as we know, a male. Finally, hermaphroditism means 

 equal abstraction of sex-potencies by the chromosomes, 

 leaving in the cytoplasm both male- and female-factors. 



These considerations warrant the assumption that the 

 genes play a part in heredity but are not the factors of 

 heredity in the sense of the geneticist; the genes act through 

 their binding of potencies in such wise as to free the action 

 of the cytoplasm-located factors of heredity — that is, 



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