209 
of the Oviviviparous Shark , &c. 
corresponding to the number of yolks that are in a state to 
leave the ovarium at the same time, are inclosed in a mem- 
branous bag, piled one upon the other. This bag, at its upper 
end, is grasped by the contraction which separates the middle 
and lower portion of the oviducts ; the other extremity, which 
is in the form of a blunted cone, is loose and moveable in the 
surrounding cavity ; the eggs are inveloped in a transparent 
jelly, which occupies every part of the bag, beyond that in 
which the eggs are contained. 
The clitoris becomes so much enlarged as to project exter- 
nally ; its base swells out into the form of a heart, as it is painted 
upon cards, only that it is much more pointed ; the posterior 
surface adheres closely to the parts behind it, for one half of 
its length, the other half is loose, and on its upper surface 
there is a groove passing on each side, towards the orifices of 
the two oviducts. The nymphae are formed by a fold of the 
termination of the rectum, and project laterally ; they are very 
vascular, and compose the external orifice of the vestibulum, 
beyond which are the contracted openings of the oviducts. 
After impregnation has taken place, the pendulous portion of 
the clitoris becomes flaccid and narrow. 
When the young dog-fish is completely formed, the yolk 
remains attached to the belly by a long chord, consisting of 
blood vessels, and the fish swims about in the surrounding 
jelly with this attached to it. If the bag is torn, and the fish 
is taken out and put into water, it swims about, but if the 
vessels going to the yolk are wounded, the fish immediately 
dies. 
What number of the shark tribe have this particular mode 
of hatching their egg s is not at present known, but there is* 
