ABNORMAL MITOSES IN SPERMATOGENESIS. 185 



There are obviously three possible types of abnormal cell divi- 

 sion, which may be outlined as follows : 



Case i.- -The number of chromosomes is normal, but the num- 

 ber of centrioles is abnormal. 



Case 2.- The number of centrioles is normal, but the number 

 of chromosomes is abnormal. 



Case ?. The number of both chromosomes and centrioles is 

 abnormal. 

 Examples of these three cases will be considered in order. 



CASE i. 



The occurrence of dividing cells in which a normal number of 

 chromosomes is arranged on a multipolar spindle is very rare. 

 Indeed, I have found only a single case of this kind, and do not 

 recall having noted any similar cases in the published work of 

 other writers. This unusual example was found in a testis of 

 Chcllnidca vittigcr Uhl. (Family Corcidcc), which did not present 

 any other unusual features. In the male of ClicUnidca the sper- 

 matogonial chromosomes number twenty-one, of which two are 

 very small so-called m chromosomes and one, an unpaired X 

 chromosome. In the first maturation division the chromosomes, 

 eleven in number, are arranged in the manner characteristic of 

 other coreids. 



The abnormal division here reported occurs in a cyst of sperma- 

 tocytes in the metaphase of the first maturation division. The 

 spindle is tri-polar (Fig. 3) and the centriole at each pole can be 

 distinctly identified. The legs of the triangular spindle figure are 

 nearly but not quite equal ; otherwise it is very regular in forma- 

 tion. The eleven chromosomes characteristic of this division can 

 be easily counted, and in most cases their distribution to the 

 spindle poles can be foretold. Their arrangement on the spindle 

 is very regular, and it will be readily seen that each pole of the 

 spindle will receive approximately the same number of anaphase 

 chromosomes. In the figure the chromosomes are numbered ac- 

 cording to the approximate level of focus at which they appear, 

 No. i being the topmost (the two topmost chromosomes (No. i) 

 were added from a contiguous section). 



The disposition of the tn chromosomes is particularly interest- 



