FORMATION OF THE FIRST SPERMATOCYTE CHROMOSOMES 565 





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B 



•••.•• 



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D 





E 





•;••• 



!••• 



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•In 



i? 



G 



H 



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K 



M 



N 







Fig. 3 Specimen 29-2. A, a resting nucleus between the first and second 

 spermatocyte divisions; B, C, second spermatocyte divisions, polar views, 14 

 chromosomes; D, E, F, the same with 13 chromosomes; G, H, the same with 12 

 chromosomes; I, J,K, the same with 11 chromosomes; L, M, N, 0, P, anaphases of 

 the second division, side view, showing the behavior of the lagging chromosomes. 



If there are 12 bivalents in the first division, all of them divide 

 so that each secondary spermatocyte receives 12 chromosomes, 

 and by actual count it is seen that more than two-thirds of them 

 receive this number. When there are 13 chromosomes in the 

 first division, two of these are univalent and divide irregularly. 

 If both divide, each resulting cell receives 13 chromosomes; 



