SHARKS. 
303 
weaker and more easily ruptured than any other 
part; a provision for the easy exclusion of the 
animal^ which takes place before the entire 
absorption of the vitellus or yolk of the egg, the 
remainder being attached to the body of the 
young fish^ enclosed in a capsule, which for a 
while it carries about. The position of the ani- 
mal, while within the egg, is with the head 
doubled back towards the tail, one very un- 
favourable for the process of breathing by in- 
ternal gills, and hence there is an interesting 
provision made to meet the emergency. On each 
side a filament of the substance of the gills 
projects from the gill-opening, containing vessels 
in which the blood is exposed to the action of 
the water. These processes are gradually ab- 
sorbed after tl;e fish is excluded, until which the 
internal gills are scarcely capable of respiration. 
How curious an analogy we here discover with 
the Frogs and Newts among the Reptiles ; and 
how impressively do we learn the Divine benevo- 
lence, when we find that the object of so much 
contrivance and care is the dreaded and hated 
Shark ! 
In some species the horny capsules in which 
the young are enclosed at birth are destitute of 
the filamentous prolongations of the angles ; in 
some they have but two projecting points, one 
end being rounded ; while other species, as 
the Penny Dog {Galeus vulgaris^, and Smooth 
Hound, {Mustelus IcEvis), of our own shores, bring 
forth their young alive and fully formed, without 
any capsule or covering at all. 
A hundred and fourteen species are reckoned 
by Prince Bonaparte to belong to this Family; 
