THE SPERMATOGENESIS OF AGALENA N.EVIA. I2/ 



somes, having reached their definitive form, become more com- 

 pact and densely staining and spindle fibers appear (Fig. 23). In 

 metaphase all of the double V's are drawn into the equatorial 

 plate and the plane of division passes through the center of each, 

 giving rise to single V's which are carried to the opposite poles. 

 The accessory chromosomes lie at the periphery of the equatorial 

 plate and are connected by spindle fibers to one pole only, a 

 single fiber passing from the centrosome to each of the two rods. 

 In the succeeding division they pass into but one of the two 

 daughter cells, so that we find half of the secondary spermato- 

 cytes with accessory chromosomes and half without them (Figs. 

 24-26). Those containing the accessory chromosomes might 

 be called " favored cells " (" bevorzugten zellen ") as suggested 

 by Henking. In polar views of the telophase several sections 

 were found in which each of the two accessory chromosomes 

 showed a distinct longitudinal split a precocious splitting 

 which is of interest as foreshadowing the division which occurs 

 in the following mitosis (Fig. 27). 



While the arms of the V-shaped chromosomes are elongating 

 and becoming sinuous or twisted in outline, a conspicuous cell- 

 plate forms and the constriction of the cell body grows deeper 

 (Fig. 28). Since the chromosomes are long and twisted at this 

 stage it is plain that even in fairly thin sections there might occur 

 more than one section of a single chromosome and therefore little 

 dependence could be placed upon the number counted in succes- 

 sive sections of the same nucleus. Figures 29 and 30 show the 

 next stage with the accessory chromosomes in longitudinal and 

 cross section respectively. The nuclear membrane has formed, 

 the chromosomes are resolved into granules distributed on the 

 nuclear reticulum and complete division of the cell body gives rise 

 to two daughter cells, the secondary spermatocytes. Even at a 

 very late stage of this process remains of the interzonal fibers, 

 with the cell-plate, are conspicuous. In the late prophase of the 

 secondary spermatocytes there arises from the preceding resting- 

 stage a number of slender, twisted chromosomes closely resem- 

 bling those which entered the resting stage and not infrequently 

 the accessory chromosomes show a precocious, longitudinal split 

 (Fig. 31). As the ordinary chromosomes are drawn into the 



