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 loosefrom 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. Giinther, 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 Percide): 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 
eall 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 
