174 RAYMOND BINFORD 
from the ovary of Menippe mercenaria, I found a few spermatozoa 
attached, as shown in figure 96, with the nuclear cup next to 
the shell of the egg. That the eversion of the capsule does not 
force the nucleus through the shell in this case is shown in figure 
97, where a spermatozoon has exploded with the nuclear cup 
against the egg. So far as my observations go there is no evi- 
dence whatever that the eversion of the capsule causes any 
sudden movement of the spermatozoon body as a whole. 
The number of spermatozoa which have pierced the shells of 
the eggs is much greater for eggs taken from the oviduct than 
for those taken from the lumen of the ovary. The number was 
counted in a few eggs which had just been spawned and the 
number per egg was as follows: 28, 44, 52, 52, 54, 71, 73 and, 
in one exceptional case, 679. 
So far there seems to be no doubt as to the behavior of the 
spermatozoon in entering the egg, but we may ask: Is this the 
final stage in the entrance of the spermatozoon? Is not the 
nuclear cup drawn through the shell at a later stage? If not, 
what becomes of it? 
That the nuclear cup does not enter the egg, but falls off is 
shown in figures 98 to 101. Here we see that the nuclear cup 
has moved, away from the egg-shell and that a strand of some 
substance, by which it was probably attached to the bottom of 
the capsule, is drawn out with it. Sometimes the nuclear cup 
breaks loose from the strand and leaves it projecting through 
the shell into the capsule (fig. 100). In eggs taken from the 
oviduct or from the pleopods just after spawning, large numbers 
of sperm-vesicles are found sticking to the inside of the shells 
after the nuclear cup has fallen off (fig. 101). It is very clear 
then that, in most cases at least, the nuclear cup does not enter 
the egg. But does it thus fall off from the particular sperma- 
tozoon which fertilizes the egg, or only from those which have 
failed to perform the work of fertilization? This question can 
best be answered by a further study of the events of fertilization. 
