ICHTHYOLOGY. 



553 



for this 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 absorbed after the fish is excluded, until 

 which the internal gills are incapable of respiration. This pre- 

 sents an analogy with the Frogs and Newts. We advert to it 

 thus particularly as impressively manifesting the Divine benevo- 

 lence when the object of so much contrivance and care, is the 

 dreaded and hated SHARK ! The horny cases just referred to 

 are frequently found on the sea-shore, and are called Sea-Purses, 

 Mermaids'-Purses, &c. Some species, as the PENNY DOG, Galeus 

 vulgaris, and the SMOOTH HOUND, (Mustelus favis,) bring forth 

 their young alive, without any capsule or covering at all. 



Some species, as the Pipe-fishes, (Syngnathus,) are ovo- vivipa- 

 rous. What is very singular, the male Pipe-fish is provided with 

 a pouch, into which he receives the spawn as it is deposited by his 

 mate, and in which he carries it about until the young are 

 hatched. And, as if to make the resemblance to the Marsupials 

 complete, the young are in the habit of retiring for shelter into 

 the paternal pouch, for sometime after they are able to leave it 

 and roam at their own pleasure. It is somewhat remarkable, 

 that it is the male, generally, who assumes the care of the eggs, 

 and the construction of the nest. Instances are not wanting, of 

 striking parental devotedness and foresight. 



The following Table of Mr. Harmar, (Phil. Trans.,) shows 

 the different degrees of fecundity in different species of fishes. 



But far more productive than these, is the Salmon, (Salmo 

 Salar,) for " the ovarium of one female, has been -known to pro- 

 duce 20,000,000 eggs!" 



Prof. Dana estimates the greatest number of eggs in the Thick- 



