762 THOS. H. MONTGOMERY, JR. 
phenomenon in insects, and judging from Meves’ (00) figures of 
Paludina, the sperm head would appear to shrink there also. 
. In Euschistus it is at about this stage that the idiochromosome, 
up to that time very distinct in the centre of the nucleus, dis- 
appears from view, either it is then discharged from the nucleus, 
or else it then becomes so changed physically that it can no longer 
be recognized. Now we know that allosomes invariably enter 
into the composition of the sperm nucleus, and generally occupy 
a position near its middle, from the studies of Henking, Gross, 
Otte, Buchner, Gérard (’09), Davis, Paulmier, Stevens (’05, ’06, 
10), Boring and Wallace (’09). Some of these investigators 
have been able to trace the allosome only during the earlier part 
of the histogenesis of the sperm, and so far as I can learn no one 
has been able to identify it within the mature sperm. But some 
have beén able to distinguish it within the sperm head after the 
nucleus has contracted, as Henking, Gross (’06), Jordan, and Otte, 
and we know positively from the studies of Morrill (10) that 
the sperm carries allosomes into the egg. By analogy with these 
cases it may be that the idiochromosome of Euschistus remains 
within the sperm nucleus even after the latter has discharged 
substance, but whether it does or not it certainly disappears from 
view at that time. 
THE PLASMOSOMES 
A. Observations 
These were correctly described Py me in 1898 and there is 
little to add to that account. 
In the spermatogonia one or two occur in the resting nucleus 
(figs. 1 and 3). In the spermatocytes they may be readily dis- 
tinguished from the idiochromosomes by their staining reactions 
and form: they stain brown or pale violet and the idiochromosomes 
red after Hermann’s triple stain, and, after Delafield’s haematoxylin 
and eosin, they stain red and the idiochromosomes blue. With 
iron haematoxylin they may either stain as deeply as the idio- 
chromosomes or paler, dependent upon the degree of extraction 
, 
