392 HARRY H. CHARLTON 



time the telophase is reached, and it would appear as though 

 this thread were fused with the smaller idiochromosome so 

 that they both appear equal in the metaphase of the second 

 maturation division. Another factor in favor of this hypothesis 

 is that the chromatic nucleolus of the resting stage shows a double 

 structure with hardly any inequality. 



In the early anaphase (fig. 55) all the chromosomes show a 

 longitudinal split near their centers, except two which represent, 

 I believe, the divided idiochromosomes. The anaphase often 

 shows the chromosomes arranged in the form of a ring (fig. 62). 

 In figure 63 the chromosomes are at the poles and are beginning 

 to form a nuclear membrane, but no change has taken place in 

 the centrosomes. Figure 60, a late telophase, shows that one 

 chromosome differs from the rest in being elliptical, while the 

 others are V- or U-shaped and slender. A still later telophase 

 is figured in figure 61, the chromatin now being massed at the 

 poles. Two types of spermatids are formed, those with sixteen 

 and eighteen chromosomes, respectively. 



The centrosome in the spermatogonial and maturation divisions 



In the archoplasmic mass or sphere representing the remains 

 of the previous spindle one may occasionally see two dark gran- 

 ules (fig. 18), which I take to be the divided centrosomes. In 

 the division figures of the spermatogonia centrosomes are difficult 

 of demonstration, but in a few slides I can make them out as 

 definite single granules at the poles of the spindle (fig. 12). I 

 have never seen astral rays or anything comparable to a centro- 

 sphere at the time of division, but during the resting stages the 

 centrosome is found in a granular sphere. 



From the division figure of the last spermatogonial mitosis 

 until shortly before the synaptic or contraction stage, the centro- 

 some has not been traced, and when it does appear a considerable 

 metamorphosis has taken place. At about the time when the 

 fine spireme threads are being changed into loops, a granular 

 mass can be made out at one end of the cell, and in this mass 

 appear two short, stubby rods lying parallel to each other. 



