DANFORTH: NEW PTEROPOD. 17 
somewhat obliquely downward and backward so that its posterior 
end lies near the left pedal ganglion. It is enclosed in a sheath as 
indicated in figure 14 (pi. 4) which shows the general appearance in a 
section cut in the horizontal plane. In this section may be noticed the 
characteristic large nuclei of the inner wall of the penis and also its 
deeply staining outer fibrous layers. When retracted the penis has its 
anterior end a little below the surface of the body, thus opening into a 
kind of cavity which communicates with the exterior at fo (pi. 2, fig. 6). 
Opening into this same cavity is a large gland, a section of which is 
shown in figure 14, pg 1 (pi. 4). Indeed, the cavity into which both the 
penis and this first penial gland open, appears almost as an excurrent 
duct leading from the gland to the exterior. If it were to be thus 
regarded the penis would have to be described as opening into this 
duct just before the latter reaches the exterior. That this gland is 
really related to the penis is shown by the fact that it reaches its greatest 
size at a time when the penis is apparently in a condition to function. 
When the gland enlarges it pushes down into the body till its lower 
portion comes to lie near the vagina. Its cells are prismatic in form 
and in the functionally male specimens, distinct in outline as shown 
in the figure. 
Connected with the hinder end of the penis is a second penial gland. 
This gland is of small size when not functioning, but as it enlarges it 
pushes backward and downward till it has partially enveloped the 
esophagus and come to lie in part inside the neural ring. Like the 
first penial gland it may reach nearly to the vagina. The condition in 
the specimens studied is such that I can make almost nothing of its 
finer structure. In section (pi. 4, fig. 14, pg^) it appears as a simple 
sack with glandular walls. It is filled with a substance which is 
generally clear and homogeneous in the center but denser and more 
heavily staining near the walls. W'hich of these glands, if either, is 
homologous with the "prostate" gland described for some of the 
Gastropods I am unable to say, although it might seem to be more 
probably the second, inasmuch as that gland is directly connected with 
the penis. 
From the foregoing description it may be seen that all of the organs 
connected with the reproductive system do not function at any one 
time. Consequently, since the specimens sectioned were in various 
stages, I am able to summarize what seems to be the sequence of their 
activities as follows. 
