SEXUAL ACTIVITIES OF THE SQUID 391 
heres to the inner membrane covering the cement body firmly, 
and in ejaculation is liberated only by the rupture of this mem- 
brane. It is important to understand that the open mouth of 
the middle membrane is directed aborally and the open mouths 
of the inner tunic and the outer membrane are directed orally. 
The one fits inside the other. The oral end of the middle mem- 
brane is a closed structure, like an indented hollow rubber ball, 
attached by its margin to the outer tunic and with the thin con- 
vex side (fig. 2, MM‘) applied to the under surface of the cap 
which closes the outer tunic. This part ruptures when the cap 
is loosened, so the lumen of the ejaculatory apparatus is opened 
to the outside (fig. 5, MM"). 
9. The inner membrane and spiral filament are united to the 
middle membrane. Their positions and relations are better 
shown by figures than by description. In-ejaculation the inner 
membrane ruptures at the point where it joins the cement body 
(fig9, PH): 
With these points in structure in mind we can now proceed 
with the method of ejaculation. 
EJACULATION 
In delivering the spermatophores the male grasps a bundle 
of them with the tip of the left ventral arm and quickly passes 
them into position (Drew, ’11). The spermatophores leave 
the sexual duct of the male aboral ends first and the long threads 
connected with their caps, embedded in the secretions of the 
spermatophoric sac, drag behind. The sharp pull occasioned 
by the movement of the arm pulls on these threads and causes 
the caps to loosen. This starts the process of ejaculation. 
Under normal conditions the process is very rapid, occupying 
about ten seconds. This very rapid action of course makes it 
impossible to follow the ejaculation under a microscope even 
though the spermatophore is held in position and the thread 
pulled when all is ready. It was accordingly necessary to devise 
some method to slow down the movements. 
Evidently the great tension of the elastic outer tunic has much to 
do with the process of ejaculation. Inasmuch as spermatophores 
THE JOURNAL OF MORPHOLOGY, VOL. 32, NO. 2 
