392 GILMAN A. DREW 
carefully removed from the spermatophoric sac without pulling 
the cap thread and placed in sea-water are very likely to ejacu- 
late soon, and placed in fresh water will either ejaculate or burst 
very promptly, it is evident that osmotic action, in which the 
middle tunic is probably involved, plays an important part. 
Elasticity and osmotic action accordingly have to be con- 
sidered in searching for some method to slow down the action. 
It was found that formaldehyde affects probably both the elas- 
ticity and the osmotic properties, but that it evidently hardens 
the cement holding the cap, so it is very difficult to open it when 
needed, and that the various membranes of the spermatophore 
are soon so changed, possibly by hardening certain colloids, 
that ejaculation is not likely to be completed. These very prop- 
erties were, however of the umost value in the studies, for 
full-strength formaldehyde thrown on an ejaculating spermat- 
ophore will cause it to stop all action rather promptly. After 
some experience it became possible to allow the required amount 
of time to stop a spermatophore at the required stage of ejacula- 
tion by squirting full-strength formaldehyde on it just before 
it reaches the stage wanted. Such a spermatophore may then 
be stained in aqueous stains and mounted in glycerin jelly for 
study at leisure. It, of course, requires a great deal of time and 
patience to get some of the stages, but, as the figures showing 
the stages of ejaculation accompanying this paper are camera- 
lucida drawings of such specimens, it will be seen that it is pos- 
sible to get the stages by this method. 
Very many chemicals were tried to get the required slowing 
effects. Sugar. solutions were good, but the membranes were 
soon weakened so the elasticity was destroyed. Magnesium 
chloride solutions have given the best results. The strength 
of the solution that works best seems to differ with spermato- 
phores from different individuals, but a one-fourth saturated 
solution in sea-water has been very good. 
The spermatophores are received from the spermatophoric 
sac directly into this solution, and in two or three minutes they 
will be ready for use. The turgidity is evidently effected, and 
where the spermatophores are left several hours, there may be 
