NOTES ON THE OCCURRENCE OF ABNORMAL 

 MITOSES IN SPERMATOGENESIS. 



ROBERT H. BOWEN.i 



t 



Mitotic figures abnormal particularly with respect to the num- 

 ber of chromosomes and centrioles involved are, as is well known, 

 of common occurrence in the spermatogenesis of many insects. 

 Apart from their interest as mere abnormalities, these cases some- 

 times throw light on more important problems of cell division and 

 acquire, therefore, a much greater significance. In the course of 

 several years' study of hemipteran (Family Pentatoniidcs) sper- 

 matogenesis a variety of abnormal types of division have been 

 observed, and it has seemed worth while to assemble descriptions 

 of some of these, in particular those not hitherto described by 

 other workers. The cases here reported are all from the male 

 germ cells of various Hemiptera, belonging with one exception to 

 the Family Pcntatomidcc. The material was originally fixed for 

 a variety of different purposes and the methods are accordingly 

 noted separately where necessary. I am indebted to Professor 

 E. B. Wilson for the use of a number of slides of Lo.ra florida 

 which he had prepared some years ago and which I found pre- 

 sented a very unusual type of cell division. 



Abnormal mitoses occur sometimes as solitary exceptions among 

 many normal cells, but at other times they occur in large num- 

 bers in a single testis. In the latter case the abnormal cells may 

 form a large percentage of the cells in a single spermatic cyst. 

 Frequently the condition which produces these irregularities is 

 more widely operative with the result that large numbers of cells 

 in a given testicular lobe or follicle are involved. The isolated 

 cases are doubtless due to occasional ' accidents ' such as are to 

 be expected in all vital phenomena ; but the simultaneous occur- 

 rence of many abnormal divisions seems sometimes to depend on 

 other causes, the nature of which is for the most part unknown. 



i From the Department of Zoology, Columbia University. 



184 



