DEGENERATE (aPYRKNE) SPERM-FORMATION OF MOTHS. 471 
sagging of the macromitosome has caused the method of 
fixation to the centrosorne to be revealed, though how the 
other end of the spireme is attached I do not know. In the 
normal spermatid the stage drawn in PL 26, fig. 6, gradually 
passes to the stage of a tangled spireme (PI. 26, fig. 2, etc.). 
Now when the spermatid begins to elongate, the attached 
front end of the spireme remains in its position, and the rest 
of the mitochondrial matter becomes “let out ” or “ played 
out” as the elongation takes place. This process has taken 
place normally from C. to Y. in PI. 26, fig. 12, but somehow 
or other the spireme subsequently became apparently refrac- 
tory (M.), and was left in this position, while the lower part 
(Z.) made an endeavour to form normally as the elongation 
went on. In PI. 26, fig. 5,. another sort of abnormal formation 
is shown : here the macromitosome, instead of pulling out in 
a smooth, even manner, came out in lumps (ili. 1 — Iff. 6 ) . In 
PI. 26, fig. 3, the spireme is loosing its position en masse. 
It seems that the retention of the spireme in its place, or at 
least its completely normal elongation, rarely takes place 
after the failure of the nucleus to act properly. This may be 
due to the general abnormal condition in the cell. 
The Aero blast and Acrosome. 
This body can almost invariably be found in the early 
spermatid, and in those cases where its presence cannot be 
ascertained until sperm-formation is well advanced, special 
refinements of technique may succeed in demonstrating it 
early. In the case of the snail I have experienced unusual 
difficulty in studying this body. I have found that bichro- 
mate of potash is extremely favourable for fixing the acro- 
some, and osmic-bicl) rornate fixatives are indicated in this 
section of spermatogenesis studies. For instance, by smearing 
the ovotestis of Helix on a slide, momentarily fixing in osmic 
acid fumes, and then, after allowing the film to dry partially, 
dipping into a 2 to 5 per cent, bichromate of potash solution, 
an extremely intense stain of the acrosome is got if the slide 
is so;iked long enough in the bichromate solution. My work 
