560 FERNANDUS PAYNE 



From these various descriptions and disagreements, it would 

 seem that an excessively large number of errors have been made 

 or that we really have irregularities in chromosome distribution. 

 I believe the latter to be the case. In fact, my material shows this 

 beyond a doubt and offers a plausible explanation for at least 

 some of these irregularities. Stevens ('10) suggests that Forficula 

 auricularia is a composite species, made up of several small species, 

 which differ with respect to the number and behavior of the chro- 

 mosomes. With this possibility in mind, I have studied the 

 individuals singly and then compared the results. As we shall 

 see, the differences within some individuals are as difficult of 

 explanation as between different individuals. 



DESCRIPTION 



Specimen No. 29-2. In this specimen I found only one sper- 

 matogonial group which I was able to count. This showed clearly 

 24 chromosomes (fig. 1, A). The fact that the specimens were 

 collected so late in the season accounts for the small number of 

 spermatogonia! divisions. A large percentage of the testes col- 

 lected were full of mature spermatozoa. The first spermatocyte 

 divisions show 12, 13 and 14 chromosomes (fig. 1, L and M; 

 14; N, 13 and 0, 12). By counting only clear metaphase plates, 

 I found 18 cells with 12, 13 with 13 and 3 with 14 chromosomes. 

 These variations are found, not only within the testes of one 

 individual, but, contrary to the observations of Zweiger ('06), 

 they occur within a single cyst. Zweiger believed that a cyst 

 arises from a single cell and hence all cells within the cyst contain 

 the same number of chromosomes. He gives the spermatogonia! 

 number as 24 and 26. The half or reduced number would be 

 12 or 13. This, however, would not explain his 14 chromosome 

 counts. According to his view such a group would have to arise 

 from a spermatogonia! cell with 28 chromosomes. 



In my work a study of polar views failed to explain these 

 variations, so I have resorted to a study of side views of meta- 

 phase plates, and believe I have found a true explanation. Why 

 the chromosomes behave as they do thus causing these variations, 

 I cannot say. Smear preparations would no doubt have helped 



