Class IV. CARTILAGINOUS FISHES. 101 



a yolk, and is lodged in a case, formed of a 

 thick tough substance, not unlike softened horn : 

 such are the eggs of the Ray and Shark kinds. 



Some again differ in this respect, and are 

 oviparous ; such is the Sturgeon, and others. 



The young of the Shark genus will, like those 

 of the Viper, take refuge in the stomach of the 

 parent, on the apprehension of danger. If they 

 are cut out while the old one is alive, they 

 appear active and vigorous, but as they exist 

 by the air which she inhales, they cease to live 

 as soon as she ceases to breathe. I have seen 

 thirty-six, each about ten inches long, taken 

 out of the stomach of the Tope Shark. 



Cartilaginous fishes breathe through certain 

 apertures, placed either beneath, as in the Rays ; 

 on the sides, as in the Sharks, &c; or on the 

 top of the head, as in the Pipe-fish ; for they 

 have not covers to their gills like the bony 

 fishes. 



genious treatise by Everard Home, Esq. on this subject, and on 

 the aeration of the foetal blood in different classes of animals. 

 Ed. 



