PISCES. 

 Fig. 536. 



1007 



Viscera of the Herring ( Clupea harengus). 



a, oesophagus ; b, c, stomach ; d, pyloric cceca ; e, intestine ; f, anus ; g, spleen ; h, h, ovary ; t, ovi- 

 ducts ; k, air-bladder. 



ovarian capsule arises a short canal i, i, and these 

 two ducts uniting form a common tube, through 

 which the ova pass out of the body through an 

 aperture,,/, 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 mitt 

 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 naturae, although regarded by some of 

 the older naturalists as a normal occurrence. 



Among the Salmonidae 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 Syngnathida, 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 (I, I,), 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 

 (o), 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 (Jig. 

 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, (q, q,) so 

 called because they are generally supposed to 

 be used for clasping or holding the female 

 during the sexual intercourse necessary for 

 internal impregnation, although some authors 

 have imagined them rather to perform the office 

 of an intromittent organ by being actually in- 



