SPERMATOGENESIS OF EUSCHISTUS 761 
in other testes (’10a). I have made some counts to determine 
their constancy. In testis no. 265 one was seen in seventeen out 
of thirty polar views of the first maturation metaphase, but none 
in sixteen polar views of the second; in testis no. 282 one was 
observed in seven out of twenty-eight polar views of the first 
maturation. but none in twenty-seven polar views of the second. 
C. Discussion 
There are two kinds of allosomes, the minute chromosomes and 
the idiochromosomes. 
The minute chromosomes would appear to be allied to the very 
small chromosomes called by Wilson the microchromosomes of 
such forms as Anasa, but they differ from them in not dividing 
in the maturation mitoses. Minute chromosomes were described 
by me before (’10a) in another testis (no. 120) of the same species, 
and there they were frequently attached to other chromosomes 
during the maturation divisions: they were then termed by me 
‘supernumerary’ chromosomes. On account of their minute 
volumes little can be ascertained of their behavior, but the fact 
that they do not appear to divide might indicate that they are 
degenerating idiochromosomes. 
The idiochromosomes proper are not recognizable in the resting 
nuclei of the spermatogonia, for what I had previously (’01) 
supposed to be idiochromosomes in these cells I now find are the 
minute chromosomes. The idiochromosomes thus come to behave 
differently from the ordinary chromosomes first in the spermato- 
cytes, in agreement with my earliest account of 1898. 
One of the most interesting facts determined is the discharge of 
a considerable volume of material from the nucleus during the 
histogenesis of the sperm. A sudden shrinkage of the sperm 
nucleus just before it begins to elongate has been described or 
figured for a considerable number of insects, thus by Henking 
(91), Gross (04, ’06), Paulmier (99), Buchner (’09), Wassilieff 
(07), Davis (08), McGill (06), Cook (10), Jordan (’08), Pantel 
and de Sinéty (06), Boring (’07), while Otte (07) has called par- 
ticular attention to it. It would then appear to be a common 
