THE BIOLOGY OF THE CELL SURFACE 



the sperm-cell as such is differentiated from all other cells 

 and retains in its cytoplasm only the potency for sperm- 

 ness, this conditions the nullification in some way of those 

 potencies borne by the chromosomes. Or they may be 

 lost during the process of the ripening of the sperm-cell, 

 when, as is known, concomitant with morphological changes 

 amino-acids are lost. A less likely assumption is that 

 potencies of the sperm-nucleus are lost and nullified at 

 fertilization. 



In any case, both egg- and sperm-chromosomes are pre- 

 pared for removing stuffs from the cytoplasm of the egg. 

 I bring an example: If a spermatozoon from a Drosophila 

 possessing pure red-eye fertilizes an egg of an also purely 

 red-eyed female, in the cells which show redness, the egg- 

 and sperm-genes remove from the cytoplasm the hindrance 

 to the reaction leading to redness. The "factor," redness, 

 is resident in the cytoplasm and expresses itself because the 

 genes remove stuff opposing this reaction. If on the other 

 hand the sperm-chromatin is descended from a white-eyed 

 animal and the egg-chromatin from a red-eyed one, the 

 sperm-chromatin, when in those cells which give the color to 

 the eve removes stuff which releases whiteness-reaction, and 

 the egg-chromatin stuff which releases redness-reaction, 

 with the result that the cytoplasmic reaction is now no longer 

 r -f r = i? as in the first case, but r -\r w — R{zv) where 

 R{w) gives either dominant red-eye color or an interme- 

 diate color between red and white. Thus this conception, 

 whilst consonant with the experimental findings of Men- 

 delian genetics, differs from the theory of the gene for it 

 places the determination of characters in the cytoplasmic 

 reactions. The active "factors" for Mendelian characters 

 do not reside in the genes; rather, the genes by extracting 

 definite materials from the cytoplasm render possible the 

 reaction of the cytoplasm-located hereditary factors. Onl)' 

 so far as they take out substance do the genes determine 

 heredity. 



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