223 
the resulting spermatids (HEenkıng, PAULMIER). As a result of this, 
we have two forms of spermatozoa in equal numbers. 
Regarding the general distribution of the accessory chromosome 
among insects, it may be said that, aside from its precise identification 
in the Hemiptera and Orthoptera, the work of many other insect 
spermatologists tends to show the presence of such a structure in the 
spermatocytes of other orders. I have personally observed it in the 
Orthoptera, Hemiptera, Neuroptera, Coleoptera, and Lepidoptera so 
that I do not question that it is a constant element in the male germ 
cells of all insects. 
It may be noted further that it has been identified in the spiders 
(WALLACE), which would seem to indicate its general occurrence in the 
Arthropods. I have examined the cells of Cambarus but have not 
been able to identify it there. Owing to the small size and great 
number of chromosomes in the cells of these Crustaceans, however, it 
would be very difficult indeed to distinguish an individual element of 
this kind, so that failure to find it would by no means prove its ab- 
sence !). 
Also MONTGOMERY in his paper upon “The Spermatogenesis of 
Peripatus balfouri” describes a structure which I think must be the 
accessory chromosome. His reasons for thinking that it is not so are 
by no means conclusive. The first objection, that it can not be 
distinguished in the first spermatocyte mitotic figure, holds good for 
many insects; the second, that the number of these bodies is inde- 
finite, may be met by the statement that the accessory chromosome 
undergoes fragmentation in the Orthopteran cells where its genesis is 
clear; the third, that these bodies in Peripatus are early peripheral 
in position upon the nuclear membrane, is a fact in strict accordance 
with the behavior of the accessory chromosome in the Orthopteran 
cells; and the fourth, that there is a clear space (“perinucleolar”) 
around the bodies, is of little weight when it is known that the 
chromosomes of the Orthopteran cells are thus set off from the 
achromatic substance. The spermatogenesis of Peripatus would seem 
1) Since the completion of the paper of which this is an abstract, 
another of my students, Mr. M. W. Brackman, has made a preliminary 
study of Myriapod spermatogenesis (see Kans. Univ. Quart., Vol. 10, 
No. 2). In Scolopendra he is able to recognize the accessory 
chromosome in a strongly modified form. This departure from the ty- 
pical appearance of the element in insect cells is correlated with a like 
divergence in all particulars from the ordinary form of spermatogenesis, 
so that an explanation of the one must wait upon the other. 
