434 
J. bront£ gatenby. 
became quite clear (PI. 25, fig. 45). Smerinthus is a very 
favourable example for the study of micromitosome, both 
because the individual cells are large and the cytoplasm is 
not crowded with coarse granules, as is especially the case 
with Orgyia and some others. 
The Cell Processes of the Spermatocyte. 
Not long after the beginning of the growth period, and at 
a stage which varies a good deal in different species, the 
spermatocyte shows a tendency to put out cell processes. 
This tendency seems correlated with the advent of the centro- 
some near the surface of the cell (PL 23, fig. 6) ; in PI. 23, 
fig. 7, the centrosome has divided and the cell processes are 
beginning to appear. In Text-fig. 2 I have drawn a group 
of spermatocytes to show the relationship of the processes to 
the lumen of the cell-nest. The latter forms a sphere whose 
centre is hollow (L.) and into which the cell processes stretch. 
The length and character of these processes differ widely ; in 
Pierids they are extraordinarily large and clavate, in some 
cases at least one half of the spermatocyte is taken up in the 
formation of these very large finger-like projections. In 
PI. 24, fig. 22, the Pierid spermatocyte is drawn and it shows 
how extensive these processes are. In some cases it appears 
as if the processes sprung from a centre which is formed by 
the two centrosomes; in such examples the cell projections 
are arranged fan-wise, the centrosomes forming the bottom of 
the handle of the expanded fan. In most other species it is 
difficult to imagine any relationship between processes and 
centrosomes, as in Smerinthus populi. In Euchelia, especi- 
ally in early stages, the spermatocyte projects into the lumen 
in the characteristic manner (not well shown in PI. 25, fig. 45), 
the cell often being extraordinarily attenuated. In these cases 
the centrosome (at present undivided) may or may not lie in the 
single large cell process. Acetic fixatives are rather unfavour- 
able, for they tend to break up these delicate organs, and 
I am inclined to believe that such fixatives cause the cell 
