456 W. BLAXLAND BENHAM. 
have same shape as the first. The fully developed penial 
cheta (fig. 8) is 49 mm. in length, measuring as accurately 
as possible along the curve; the inner end is sharply bent 
and somewhat enlarged: the free end (fig. 9) is quite similar 
to that described by Rosa and Michaelsen. Its tip projects 
freely into the duct of the gland, the rest of it lying in a sac 
of its own with thick bundles of longitudinal muscles forming 
its walls (figs. 12—14). Each of the reserve chet lies 
in its own sac (figs. 12, 18, ch®., ch®.), but their pointed ends 
are enveloped in this sac, and do not project into the lumen 
of the duct. This seems to indicate that the penial chetz are 
lost from time to time. 
These features can be well seen in following serial sections. 
A section somewhere about the middle of the chztophore 
shows three chztz, each surrounded by a coat of circular 
muscles, with a certain amount of longitudinal muscle. Passing 
towards the body-wall, first one and then the second reserve 
cheeta disappears as the section passes beyond their points, 
while the functional cheta still persists. Now the wall of 
its follicle presents a more distinct epithelium, and approaches 
the duct of the prostate ; it becomes wrapped in the same coat 
of circular muscles as the duct (fig. 12); and further onwards 
(figs. 18, 14) the lumen of the chetophore communicates with 
the duct of the prostate. 
The penial cheetzee when mounted in glycerine appear to be 
hollow, and the transverse lines figured by Michaelsen seem to 
me to be confined to the inner surface of the apparent wall 
(fig. 9, 7.), and are not of the nature of “ornament.” The 
pointed end of the cheta is, however, ornamented in the 
same kind of way as the ordinary cheta. In transverse sec- 
tions it is seen that the axis of each penial cheta is of a 
different character from the cortical zone: the latter is yellow, 
and has the usual appearance of a cheta (fig. 14, cor.) ; it is 
evidently brittle, for it exhibits cracks across it, and is fre- 
quently torn away in sectionising. But the “ medulla” (med.) 
stains pink in borax carmine, is homogeneous, and evidently 
softer than the cortex. 
