SMALL-SPOTTED DOG-FISH. 369 



ter months. The convoluted tendrils hanging to sea-weed 

 or other fixed bodies prevent the cases being washed away 

 into deep water. Two elongated fissures, one at each end, 

 allow the admission of sea-water ; and the young fish ulti- 

 mately escapes by an opening at the end, near which the 

 head is situated. For a short time the young Shark conti- 

 nues to be nourished by the vitelline fluid contained in the 

 capsule attached to its body by the connecting pedicle, till, 

 having acquired the power of taking food by the mouth, the 

 remains of the ovum are taken up within the abdomen, as in 

 birds and some other animals. 



A curious peculiarity has been observed in the young of 

 both Sharks and Skate during a very early stage of their ex- 

 istence. From each of the branchial apertures, branchial fila- 

 ments project externally : each filament contains a single 

 minute reflected vessel, in which the blood is thus submitted 

 to the action of the surrounding medium. These appen- 

 dages are only temporary, and the blood of the fish is after- 

 wards aerated by the true gills. This very interesting disco- 

 very, which I believe is of recent date, forcibly reminding us 

 of the temporary external branchiae in the young of Batra- 

 chian reptiles in the tadpole state, has been observed by Mr. 

 Richard Owen in the Blue Shark, Carcharius glaucus, by 

 Dr. John Davy in the Torpedo, and by Dr. Allen Thomp- 

 son of Edinburgh in the Thornback. Cuvier had previously 

 noticed it, and in the Regne Animal has referred to a figure 

 published by Schneider of a very young Shark in this condi- 

 tion, for which, regarding it as the normal state of this fish, 

 that industrious pupil of Bloch had proposed the name of 

 Squalus ciliaris. 



Among the Sharks, as among the truly predacious birds, 

 the females are larger than the males ; and almost all the spe- 

 cies have received some name resembling Beagle, Hound, 



