Natural History of the Shark. 363 



occupy the same situation, and are not very different from them 

 in appearance ; they have a common oviduct, and end in uterine 

 cavities. 



Some of the viviparous Cartilaginous Fishes are fertile only on 

 one side, generally the right. The testes are made up of two 

 portions, but one only has an excretory duct, and one only of the 

 ovaria is fully developed. The tortuous passage of the vas de- 

 ferens in the male terminates in an orifice common to it and the 

 ureters, which open on a kind of papillary eminence, the intro- 

 mittent instrument for internal impregnation. The glandular 

 passage from the ovarium is much less developed in viviparous 

 than in oviparous Cartilaginous Fishes. The oviduct is greater 

 in diameter, and the wide dilated uterine cavity, lined with plicae, 

 is the receptacle in which the young in the viviparous Sharks 

 are retained after the eggs are hatched, until they are fit for ex- 

 clusion in a state of active matuiity. 



We have already spoken of the glands in the oviduct of the 

 oviparous Rays and Sharks, as a provision for forming a horny 

 shell in which to encase the egg — an oeconomy which coincides 

 with the provision in bu'ds for investing the white and yolk 

 with a calcareous covering. In some species of viviparous 

 Sharks, much more than in others, as in the Mustelus of Cuvier, 

 the walls of the uterine portion of the oviduct are so closely 

 attached to the contained ovum, as to remind the anatomist very 

 forcibly of the placental connection that exists in the Mammalia. 

 In these instances, according to Miiller, the egg in the oviduct 

 is covered only with a kind of membranous investment or chorion, 

 w^hich is as thin and delicate as the amnion of Mammalia, and 

 without apparent organization. This sacculate membrane is 

 seven or eight times as long as the vitellus, and the regularly 

 plicated walls are embraced by corresponding folds of the lining 

 membrane of the oviduct, so that there is a very intimate adhe- 

 sion between the two. With this detail we finish our anatomical 

 refei'ences to the female, but we have not done with the male. 



In the vicinity of the cloacal apertui-e are two very important 

 members, that distinguish in a remarkable manner the male from 

 the female Shark. They are anal appendages called claspers or 

 holders, and are prominent accessoiy organs in the Ray and the 

 Chimara, as well as in the Shark. They are an extension of the 

 ventral fins. A cartilage unites them with the genitals, and the 

 pieces that articulate wdth this cartilage have received names 

 which imply their structural analogy to the hind hmbs of qua- 

 drupeds. These are the femur, the tibia, the metatarsus, and 

 the OS calcis, tenninating in a sort of digit. There is a tendon 

 of the great adductor muscle, with cartilaginous pieces, that 

 represent phalanges, moved by some strong muscles on either 



