406 GILMAN A. DREW 
membrane thus covers the cement body and the outside of the 
spiral filament, to both of which it adheres firmly. Orally 
to the spiral filament, the inner membrane covers the hyaline 
core. 
A little further on the middle membrane is formed. The sheet 
of which it is formed is thin, but is wound around many times 
in building up this comparatively thick membrane. What 
causes the aboral end to be so definitely limited has not been 
determined. 
The portion of the gland immediately following that which 
forms the middle membrane forms the outer membrane and 
that which follows, as already stated, forms the inner tunic. 
All of these structures (figs 23 and 23 A), the inner membrane 
(IM), middle membrane (MM), outer membrane (OM), and 
inner tunic (/7’), are formed in the same manner and the gland 
in which they are formed shows no definite change in structure 
from one part to the other. Apparently all are being formed 
at the same time and the formation of each part stops when it 
is completed. There seems to be nothing visible that limits the 
extent of the formation of each structure. 
Some membranes adhere to others with which they come in 
contact and some do not. Thus the inner membrane forms 
a covering for the cement and adheres to the spiral filament 
and middle membrane. The outer membrane adheres to the 
inner membrane over the cement body, where they come in 
contact, and to the inner tunic, but not to the middle membrane. 
It is perhaps as well to call attenton to certain peculiarities 
in forming structures here as anywhere. The core of mucilagi- 
nous material in the sperm mass seems to be continued for- 
ward into and through the cement body (fig. 23 A). The con- 
necting cylinder between the two parts is very prominent. The 
cement is seen to be spirally wound around this core in the par- 
tially formed spermatophore and the core is continued on through- 
out the length of the hyaline core as a much smaller core. The 
hyaline core is evidently continuous with the cement material. 
The inner core does not stain heavily with any of the stains 
and seems to be distinct in composition from the cement material. 
