396 GILMAN A. DREW 
When evagination has proceeded as far as the oral end of the 
cement body, so that the end of this body begins to project 
through to the outside, the inner membrane is ruptured, so that 
this membrane, with the remnants of the spiral filament, is 
separated from the cement body (fig. 9, PR). 
As evagination now proceeds, the oral end of the cement 
body projects into the sea-water. At this point ejaculation 
is retarded until the very great pressure behind the sperm mass 
forces this mass against the aboral end of the cement body, 
to which the inner surface of the middle membrane is attached, 
and so causes the middle portion of the cement body to be drawn 
out and around the sides of the aboral portion of the cement 
body in the form of a cap (fig. 11). The extreme oral end of the 
cement body, from which the inner membrane and spiral fila- 
ment have been torn, appears as a knob or button on the other- 
wise smooth surface of the cement body. 
It may be well, before proceeding with the other changes 
-that are taking place, to call attention to the position of the 
oral portions of the inner tunic and outer membrane. In the 
evagination that has taken place the free ends of the inner tunic 
and outer membrane which originally enclosed the middle mem- 
brane have been turned back by the evaginating tube, so that 
the opening is directed toward the aboral end of the spermato- 
phore, and, together, they form the inner lining of the evaginated 
tube as it now appears. In this process the sperm mass is 
being carried through the opening of the inner tunic and outer 
membrane and is being forced into the sac formed by them (figs. 
9, 12, and 39). 
As has already been pointed out, the inner tunic and outer 
membrane are firmly attached to the sides of the aboral end 
of the cement body so, when ejaculation has proceeded to this 
point, the membrane cannot be stripped further aborally. The 
part which has been turned back with the evaginating middle 
membrane thus forms a sac, with the cement body firmly at- 
tached to the closed end, and the pressure from behind forces 
the sperm mass into this sac. 
