538 P. W. WHITING 



point toward the poles to which they are to go, and the middles 

 still touch at the equator of the spindle (fig. 86). The fibers 

 attach, as in previous stages, to the middles of the chromosomes. 



As the chromosomes pull apart in anaphase (fig. 87), the ends 

 tend to reverse their direction and to point toward the equator 

 of the spindle. A later anaphase is shown in figure 88. 



In the telophase (fig. 89) the chromosomes become diffuse, 

 especially at their distal ends. In figure 89 the spindle fibers 

 have been pushed out of place and the nuclei are at right angles 

 to each other. At a the nucleus is shown in side view. At b 

 is an optical transverse section. The chromosomes are plainly 

 visible, but I was unable to count them on account of the small 

 size of the nuclei. The telophase nuclei of the second spermato- 

 cytes become the nuclei of the spermatids. 



e. Spermatids 



The spermatid nuclei rapidly increase in size and the two 

 nucleoli of unequal size again appear, with the diffuse chromo- 

 somes radiating from them (fig. 90) . As the spermatid is chang- 

 ing into a spermatozoon, the chromosomes become more and 

 more tenuous and the nucleoli become diffuse (figs. 91 and 92). 

 One nucleolus can be seen after the other has disappeared (fig. 

 93). Figures 91, 92, and 93 are from a slide more darkly stained 

 than figure 90. In figures 94 and 95 the staining is light and 

 thus the spermatids do not show their chromosomes. The 

 spermatid in figure 95 has begun to lengthen and is larger than 

 that in 90. I judge it to be at a stage between figures 90 and 91. 



/. 'Pathological' cells 



Among the second spermatocytes and the spermatids cells 

 are frequently seen which are evidently first spermatocytes which 

 have failed to divide while the tetrads have divided. The divi- 

 sion of the tetrad into its four monads is sometimes normal as 

 in figure 94, but more frequently abnormal. In figure 95, a 

 and b have each divided into four monads. Tetrad c has formed 

 a cross, the longer arms of which have broken off, and one of 



