VIVIPAROUS FISH. 119 



but sometimes (and this not once or twice, 

 but often) have set free the young fish from its 

 dead mother. Thus prematurely cut loose from its 

 membranous prison, the infant captive, revelling 

 in its newly-acquired liberty, swam about in the 

 saltwater, active, brisk, and jolly, in every par- 

 ticular, as well able to take care and provide for 

 itself as its parent. The female external genital 

 opening is situated a little posterior to the anal 

 opening; the orifice is at the apex, and in the 

 centre of a fleshy conical protuberance, which 

 is in fact, a powerful sphincter muscle, moored, 

 as it were, in its place by two strong muscular 

 ropes, .acting from and attached to the walls of 

 the abdomen. 



Dr. Gilnther, in the British Museum Cata- 

 logue of Fishes, uses the generic title of Ditrema, 

 which I have adopted. The first glance at 

 the fish, as it lies on the table or on the beach, 

 would lead you to pronounce it a Pomotis 

 (belonging to the family Percidce) : the northern 

 Pomotis (P. vulgaris] is a good example, and 

 very common along the shores of Lake Huron, 

 where I have often caught them. Or, on the 

 other hand, you would be perhaps tempted to 

 call it a Sparus ; the gilthead (S. auratus) may 

 be taken as a type suggesting the resemblance. 

 This fish is taken in large numbers in the 



