FrSHES. So'J 



In the females of the sharks and rays, the ovaria, two in 

 number, are situate at the sides of the spine, and contain 

 ova of different sizes. From each of these proceeds an ovi- 

 duct, the anterior extremities of which are united to the 

 diaphragm and spine. Internally, these ducts are covered 

 with glandular papillae, and pass through a large glandular 

 body, after which, they dilate into a large sac, which is 

 the uterus. 



When the ova pass into the oviduct, they are carried to 

 this glandular body, which is supposed to secrete the glaire 

 or albuminous part, and afterwards conveyed to the uterus, 

 where they receive the shell. It is not determined at what 

 period the egg becomes impregnated, or in what manner 

 the operation is performed. 



Some of the species of this group are ovoviviparous. The 

 eggs, while in the uterus, are enveloped in a membranace- 

 ous bag, having the vacant spaces filled with a transparent 

 jelly. When the young are sufficiently developed, the yolk- 

 bag is taken into the belly, and parturition takes place. 



In other species of this group, which are oviparous, the 

 eggs are of a depressed quadrangular form, pointed or pro- 

 duced at the corners, and protected by a coriaceous shell. 

 The foetus is aerated in these, by means of two slits in the 

 shell, for the admission and escape of the water *. 



Oviparous Jishes zahich are hermaphrodite. — Instances 

 of hermaphroditism among fishes, were, for a long period, 

 considered rare, and always as accidental. Basteb, detect- 

 ed such an arrangement in the Avhiting, and Duhamel ob- 

 served the same in the carp. But it was reserved for that 

 able anatomist. Sir Evehard Home, to point out a parti- 



* Sir E. Home's paper " On the mode of breeding of the ovovivtjiarous 

 Shark." Phil. Trans. 1810, p. 205. 



VOL. U. Z 



