412 GILMAN A. DREW 
the region of the cap (fig. 28) will take place, but otherwise all 
is completed. 
I have not been able to determine just how the thread that 
extends free from the cap is formed. It was first seen shortly 
before the oral end of the spermatophore enters the spermato- 
phoric duct. A small glandular tube (figs. 31 to 33, Y) lies along 
the spermatophoric duct, and opens into the finishing gland 
near where this gland opens into the spermatophoric duct. The 
lumen of this duct is flattened in cross-section and the position 
of its opening is so near the point where the thread is first seen 
that I have been inclined to the belief that secretions from 
this gland form the thread. J have, however, no real evidence. 
The spermatophore passes down the spermatophoric duct 
and enters the spermatophoric sac oral end first, with the 
cap thread lying by its side. Here it reverses ends again as 
the spermatophoric sac extends posteriorly beyond the sper- 
matophoric duct a distance equivalent to the length of a 
spermatophore. 
Each successive spermatophore crowds its predecessor side- 
wise and by forcing its oral end into the posterior pointed end 
of the spermatophoric sac causes the preceding spermatophore 
to move, aboral end forward, further into the spermatophore 
sac. Successive spermatophores are thus arranged in a spiral 
manner inside the sac, and the cap threads trail back from 
their oral ends. The last spermatophore to enter the sac has 
its oral end slightly posterior to the oral end of the spermato- 
phore that preceded it into the sac. 
The walls of the spermatophoric sac are muscular, and spiral 
lamellae, extending into its interior (fig. 33 to 36, SS), keep 
the spermatophores in position, practically parallel to each 
other, but spirally arranged, with the aboral ends moving for- 
ward. The muscular action of the spermatophoric sac is evi- 
dently responsible for the most of the movements of the sper- 
matophores it contains. 
Where the spermatophoric sac joins the outer muscular duct, 
commonly called the penis (a term somewhat misleading as to 
function), the spermatophores largely lose their spiral arrange- 
