SEXUAL CHARACTERS—ELASMOBRANCH FISHES 261 
The clasper tube, not being completely closed, is a groove 
rather than a tube. The skeletal support afforded by the pro- 
longation of the basipterygium is very slight, which permits of 
the intromittent organ being the much more easily reflected. 
The rhipidion is well developed and in the form of a fan. 
The siphon sac is similar, similarly situated and similarly devel- 
oped to that of the Squalida, but its function is obviously dif- 
ferent, since its cavity is occupied by a peculiar and characteristic 
gland, well known to most observers, which almost fills the 
sac. This gland is called the clasper gland, an appellation 
which I retain, but which does not seem to me to be very happily 
chosen. To the unaided eye the gland appears as a bilobed 
structure, having a longitudinal groove running along it giving 
it a superficial resemblance to a date stone. In the groove a 
single row of papillae can be detected. Each lobe of the gland 
is compound and can be resolved into component parts. It will 
presently be seen that the papillae are the apertures of these 
components. The siphon tube, which forms the ultimate duct 
of the clasper gland, does not debouch at the apopyle, but is 
continued as a completely closed passage the whole length of the 
clasper, down to its posterior extremity, where it opens by a 
separate aperture posterior to the hypopyle. It would seem, 
then, that the highly muscular walls of the siphon sac subserve 
the function of injecting the secretion of the clasper gland into 
the female, and not that of the propulsion of spermatozoa. 
The clasper gland (figs. 10 and 11) consists of a number of 
components arranged alternately inter se on either side of the 
median groove in the same manner as the taste-buds of the 
circumvallate papillae of the mammalian tongue, so that each 
successive papilla, or exit from a component gland, belongs to a 
component of opposite sides. Thus in transverse section in 
figure 10 (which is inverted to agree with the dissection in fig. 9) 
the gland-component ducts on the (observer’s) left lead up to 
the papilla, while the ducts on the right do not lead to the same 
papilla, but are ducts of another component. The component 
glands are compound, branching in one plane. The gland cells 
lining the lumen are roughly spherical and are almost completely 
