514 University of California Publications in Zoology [Vol. 11 



many cases it could only be discerned that there were more than 

 twenty-five and less than thirty. Di.searding the latter as doubt- 

 ful, there still remained nine clear cases in which the number 

 was definitely twenty-eight, and one ease, .just as clear, in which 

 it was only twenty-three. 



Plate 25, figure 1, represents this latter and plate 25, figure 2, 

 illustrates the more usual condition. The3' are drawn from cells 

 in one section, located near each other in the same lobule. The 

 two small elements in the center of the plate in both figures are 

 quite characteristic of this stage, and, although they cannot 

 always be found oceupjdng the same relative position, and maj' 

 sometimes be widely separated, they can u.sually be identified 

 with chromosomes of the same general size and shape lying within 

 the ring in other spindles. The chromosomes appear to be band- 

 shaped and are usually bent into the form of a letter U with 

 the free ends pointing outward. There is considerable variation 

 in size and shape and in their position with reference to the 

 spindle. 



A split can frequently be discerned in the chromosomes of 

 the equatorial plate, as is shown by several elements in the cells 

 figured. It is believed that this is evidence that the plate is 

 fully formed and that division is about to occur. Many dividing 

 cells are situated in the immediate vicinity of these two. 



The significance of the lesser number shown in figure 1 is 

 not known, nor is it possible to say just how widely such varia- 

 tions occur. In the case under consideration there is no evidence 

 that the condition is in any sense abnormal, for it does not difi'er 

 from the others except in the number of chromosome.s. This 

 plate lies in a section twelve micra thick, and the following 

 section shows only a few tips in the remainder of the cell. 



Although such exceptional cases certainly exist, even a casual 

 exploration of the lobules of dividing spermatogonia will con- 

 vince one that in a large majority of eases more chromosomes are 

 present than are delineated in figure 1. In view of the fact that 

 in every clear case found, with the exception noted, twenty-eight 

 definite elements could be made out, it seems justifiable to say 

 that the number of chromosomes in the equatorial plate of 

 Aneidcs is usuallv, but not universally, twenty-eight. 



