PISCES. 
1007 
Fig. 536. 
Viscera of the Herring ( Clupea harengus ), 
a, esophagus ; b,c, stomach ; d, pyloric ceca; e, intestine ; f, anus; g, spleen; h, h, ovary; i, ovi- 
ducts ; k, air-bladder. 
ovarian capsule arises a short canal #, 7, and these 
two ducts uniting form a common tube, through 
which the ova pass out of the body through an 
aperture, f, situated immediately behind the 
anus. 
In the male the disposition of the genera- 
tive organs is precisely similar, the membrane 
contained in the two capsules secreting milt 
instead of spawn, which when expelled through 
the efferent duct and thus mixed with the water 
in the vicinity of the ova of the female, pre- 
viously deposited, impregnates them by asper- 
sion. Instances are recorded by Cavolini and 
others of a remarkable kind of hermaphrodism 
occasionally met with in Fishes presenting this 
type of structure, in which, while the generative 
capsule upon one side of the body contained a 
roe-secreting membrane, that of the other fur- 
nished milt, so that one half of the fish was 
male and the other female; such an arrange- 
ment, however, can only be looked upon as 
a lusus nature, although regarded by some of 
the older naturalists as a normal occurrence. 
Among the Salmonide a very interesting ar- 
rangement of the generative apparatus is met 
with, which would seem to offer an intermediate 
condition between that of the Lamprey and that 
of the ordinary osseous Fishes. In the Trout 
and Salmon for instance, the extensive folds of 
the ovarian membrane are only partially en- 
closed in an investing capsule, the interior of 
which communicates by means of a wide slit 
with the abdominal cavity. In the common 
Salmon (Salmo Salar, Linn.) the ovary is much 
reduced in its relative size when compared with 
that of the Lamprey or of the Eel, although the 
ova are still developed in the folds of an irregu- 
larly transversely plaited membrane. These 
folds and their contained ova are, however, en- 
veloped on their posterior and lateral aspects by 
a thin capsule, which is wanting on their ante- 
rior surface. Through this anterior opening in 
the capsule the ova are discharged into the 
cavity of the abdomen, whence they are finally 
expelled through the peritoneal apertures 
situated near the anus, as in the Lamprey. 
Notwithstanding that the great majority of 
the osseous Fishes shed their spawn to be im- 
pregnated out of the body, some rare instances 
are met with in which the females are vivipa- 
rous, producing their offspring not only already 
hatched, but even considerably advanced *in 
growth. Such, for example, is the Viviparous 
Blenny. In cases such as these it is evident 
that impregnation must occur internally, and 
accordingly a kind of copulation must be 
presumed to be effected. Yet, even in these 
Fishes no very obvious peculiarity is to be de- 
tected in the structure either of the male or 
female organs; neither is the male better pro- 
vided with an intromittent apparatus than the 
ordinary oviparous genera. 
The Syngnathide, or pipe-fishes, offer a very 
peculiar conformation, which is not inaptly 
comparable to what is met with among the mar- 
supial Mammalia, namely, a pouch wherein the 
ova are carried about until after they are hatched, 
and in which the young are defended during the 
earliest period of their growth. 
In the plagiostome cartilaginous Fishes the 
arrangement of the generative apparatus of both 
sexes is of a very different character, approxi- 
mating that type of structure which is common 
to the Reptilia and Birds. In the male Shark 
(Squalus acanthias), which may be taken as an 
example of the group, the anatomy of these 
parts is as follows. The testes, two in number, 
(for the minute structure of which the reader is 
referred to our preceding article GeNERATION, 
ORGANS oF, Comp. Anat.) are situated at the 
anterior part of the abdomen, on each side of the 
mesial line, (fig. 537, k,) where they are at- 
tached by their inner margins to a duplicature 
of the peritoneum, which connects them with 
the region of the spine. The vasa deferentia 
derived from each of these glands are long and 
tortuous tubes (/,/, ), increasing in size as they 
pass backwards towards the cloaca, into which 
they open by an orifice common to them and to 
the ureters upon a kind of papillary eminence 
(0), which is here in truth a rudimentary penis 
adapted to facilitate the impregnation of the 
female which takes place internally. 
The openings communicating between the 
cloaca and the cavity of the peritoneum (fig. 
537, p, p,) are situated a little lower down 
beneath a kind of valvular fold formed by the 
termination of the rectum. 
In the vicinity of the cloacal aperture are 
situated the claspers, or holders, (g, g,) so 
called because they are generally supposed to 
be used for clasping or holding the female 
during the sexual intercourse necessary for 
internal impregna‘ion, although some authors 
have imagined them rather to perform the office 
of an intromittent organ by being actually in- 
