:-i 



PROCEEDINGS [IE AMERICAN ACADEMY, 



Aa the spermatocyte enters the prophase of the first maturation 

 division the oentrosome, lying in contact with the cell membrane, 

 divides, and the two daughter centrosomee move apart (Figure l) 



until they arrive ;it opposite 

 poles <>f the cell (Figure 2). 

 Although the centrosomes dur- 

 ing their initiation seem to 

 iniluence to some degree the 

 form of the cell, this modifies 

 t i< tn in outline is not so promi- 

 nent as in the honey bee. The 

 nucleus continues to lie close 

 to that one of the centro- 

 somes which in the cells ol 

 the honey bee we have desig- 

 nated as the distal centrosome 

 (Figure 2, dst.). 



The stages. immediately fol- 

 lowing this correspond strik- 

 ingly to those of the honey bee. 

 The chromatin, alter passing 

 tli rough a spireme condition, 

 gives rise to chromosomes 

 which lie scattered irregularly 



through the nucleus (Figure 

 Fn.i sua 1-1. Primary spermatocytes. X , v • 



.j N „, •_'!. We nave not as yet suc- 



Fioi i:i. 1 The two centrosomes moving ceeded in determining the 



apart; x, interzonal body. L . xart Dumber of the chromo- 



FI0UKB2 Centrosomes at opposite poles Bome8> but believe that it is 

 or cell; nucleus snowing chromosomes ; prx., 



proximal centrosome; </««., distal centrosome. Ilut lesa tlla " sixteen. 1 he 



Figure 8 First spindle figure with intra- nucleus now elongates, finally 



nuclear Bpindle fibres. becoming more or less spindle 



Figure 4 Interzonal body at proximal sh . d ]m{ apparentl y fai i s 



pole, immediately before it.- abstriction ; ' . . • i i 



r p indle figure disappearing, and extranuclear { " n ' ;irli ,h0 proxunal pole of 



fibres prominent. the cell. Intranuclear spindle 



fibres staining in iron haema- 

 toxylin have meanwhile made their appearance, extending from the 



chromosomes first to the distal centrosome, and Liter in the opposite 



direction, to a region near the proximal end of the nucleus, it being 

 novi difficult to determine the exact extent of the nuclear membrane 

 Thus the proximal ends of the spindle fibres often appear to converge to 

 a point at some distance from the corresponding centrosome (Figure 



