HEREDITY 



parthenogenesis under unfavorable conditions, 

 just as in rotifers, but the reduction which 

 occurs before development begins is partial 

 only. A whole set, N, of chromosomes is not 

 eliminated in maturation, but only 1 or 2 chro- 

 mosomes. Hence the male condition here is 

 2 N — 1 or — 2. The condition of the gametes 

 formed, however, is N in both sexes. In 

 spermatogenesis, division of the germ-cells 

 takes place into N and N — 1 daughter cells, 

 but the latter degenerate (like the non-nucleated 

 cells of the bee and wasp), and only the former 

 produce spermatozoa. Hence in fertilization 

 only 2 N zygotes are produced, which are in- 

 variably female. 



Summarizing the three categories described, 

 we may say that in all known cases of par- 

 thenogenesis, the female is in the duplex, 2 N 

 condition, the male in the simplex (N) or par- 

 tially duplex condition (2N — 1, or 2N — 2). 

 The female in all cases has the greater chro- 

 matin content. 



In a great many insects and other arthro- 

 pods, which are not parthenogenetic, it is 

 known that, although the male, like the female, 



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