384 GILMAN A. DREW 
inner tunic is seen here as a thin sheet surrounding this cylinder 
and extending from the sperm mass to the cement body. 
On the cement body the inner tunic becomes applied to the 
outer membrane (fig. 2, OM) which covers this body. From 
this point on the inner tunic (/7’) is thicker and very easily 
seen. It, together with the outer membrane, to which it is 
closely applied, leaves the cement body where it abruptly narrows 
and continues toward the oral end of the spermatophore nearly 
to its extremity, as part of the ejaculatory apparatus. The 
two structures are very similar in appearance, but the dividing 
line between them is distinct. 
Just before reaching the point where the ejaculatory apparatus 
is thrown into loops, both the inner tunic and the outer mem- 
brane thicken to form a distinct ring. The dividing line between 
the two structures is easily followed for some distance into the 
thickening and is then hard to trace. I find, however, in the 
forming spermatophore, and occasionally in completely formed 
specimens which have been mounted some months in glycerin 
jelly, that the line of separation can be indistinctly traced nearly 
through this thickening, and I am inclined to think that the 
oral end of this thickening may be taken to be the extremity of 
the inner tunic. Beyond the thickening there is no indication of 
a double character and this part is probably the continuation 
of the outer membrane only. In the thickening the two struc- 
tures are evidently more closely applied than elsewhere if, indeed, 
they are not fused. 
The free end of the outer membrane is further on among the 
loops of the ejaculatory apparatus. It is easily seen in a speci- 
men which is cut so that the loops of the ejaculatory apparatus 
straighten out, (fig. 3). This free ending of the inner tunic and. 
outer membrane on the ejaculatory apparatus is of importance 
in studying the method of ejaculation. 
The middle and inner tunics are entirely separate from one 
another. Where they touch they do not adhere. Between 
them is an actual or potential space (figs. 1 and 2, SL) filled 
with clear liquid. This space is always visible behind the sperm 
mass, in the region of the cement body, and along the ejacu- 
