DAVIS: SPERMATOGENESIS. 137 
d 
the rest stage between the two maturation mitoses.” In the present 
state of our knowledge it seems impossible to homologize this element 
with the monosome. In the case of Periplaneta Moore and Robinson 
(:05) have denied the presence of the monosome. ‘The deeply staining 
body which can be seen applied to the nuclear membrane during the 
growth period they believe to be a plasmosome, which is extruded 
from the nucleus during the prophase of the first division. ‘This 
seems in the highest degree improbable, since Stevens (:05*) has 
found a typical monosome in the closely related germs Blatella. It 
seems probable that Moore and Robinson have confused the mono- 
some and plasmosome. I have noticed that in many of the Acrididae - 
during the late growth period, when the monosome stains less deeply 
and is usually greatly elongated, the plasmosome tends to take the 
chromatin stain and appears very similar to the monosome at an 
earlier stage. Baumgartner (:04) has noticed in Gryllus a similar 
tendency for the plasmosome to take the chromatin stain. 
Recently Foot and Strobell (:07) have denied the presence of a mono- 
some in Anasa, where it had been described by Wilson and.by Mont- 
gomery. Foot and Strobell maintain that in the spermatogonia of 
Anasa there are twenty-two chromosomes, not twenty-one as held by 
Wilson and by Montgomery, and that the deeply staining element 
which is present in the spermatocytes during the growth period is 
simply a plasmosome, which is extruded from the nucleus in the pro- 
phase of the first division. ‘They have failed to find any chromosome 
which does not divide in both divisions. However, Wilson (:07) 
asserts that reéxamination of his preparations has confirmed the accu- 
racy of his’ previous results. 
I think there can be no doubt that a monosome occurs in most of 
the Orthoptera. The cumulative evidence of a large number of 
investigators cannot be lightly put aside. I fail to see how in many 
cases a more conclusive demonstration could be desired. This is 
especially true of Steiroxys, where I have been able to follow the 
monosome continuously from the primary spermatogonia to a late 
stage in the metamorphosis of the spermatid. 
In the spermatogonia of the Orthoptera the monosome is always 
one of the larger chromosomes and sometimes may be much larger 
than any of the autosomes. ‘This is the case in Xiphidium (McClung, 
799), Orphania (de Sinéty, :01) and Gryllus (de Sinéty, :01; Baum- 
gartner, :04; Gutherz, :07). In the spermatocytes the monosome 
is always a conspicuous element, where, at least in the early growth 
stages, it forms a more or less compact body applied to the nuclear 
membrane and often in close connection with a plasmosome. 
