408 GILMAN A. DREW 
and inner tunics so the two do not adhere at any place. The 
middle tunic is of about uniform thickness over the part occupied 
by the sperm mass. It is thinner and less granular from this 
point to the oral end (figs. 23 and 23A, MT). 
The forming spermatophore apparently remains in this part 
of the organ for some time; the sperm mass, cement body and 
part of the ejaculatory apparatus lying in the middle tunic 
gland, and the forward part of the ejaculatory apparatus lying 
in the ejaculatory apparatus gland. At this time the forming 
spermatophore is very much larger than the completed structure. 
It is sticky and soft so that when it is removed from the organ 
it remains bent in any shape in which it is placed, provided the 
bends be not abrupt. Before it is completed and functional, 
the forward end becomes much folded so the length is greatly 
decreased and all is shrunken so it is much less in diameter. The 
shrinking must effect length as well as diameter. All these 
changes are associated with putting on the outer tunic. 
Before leaving the middle tunic gland, mention should be 
made of a narrow tube that joins its distal end (figs. 31, 32, and 
34, X). The lumen of this duct is lined with epithelium lying 
directly on connective tissue. The walls are not glandular and 
the epithelium, which is ciliated, is evidently not composed 
of actively secreting cells. I am unable to assign any function 
to this tube. It has been suggested, by Marchand, that it may 
represent a degenerated part of the originally paired sexual ducts, 
only the left of which is functional. I have no information that 
throws light on this subject, but the point of junction in the 
course of a highly modified section of the duct is not what might 
be expected if this were the case. 
I have not been able to observe the actual formation of the 
outer tunic. In the specimens I have examined the outer tunic 
is never present while the forming spermatophore is in the mid- 
dle tunic gland. The outer tunic is always present in a sper- 
matophore that has reached the next large division, which, 
though I am not entirely sure of its function, I call the harden- 
ing gland (figs. 29 to 36, HG). Marchand speaks of this gland 
as the accessory gland (prostata), a term with no functional 
