in the Fish Gallery of the Indian Museum, 33 



the Sharks and Rays, as well as in a few species of 

 Bony fishes, the eggs are impregnated by the male before 

 they are laid, as in the manner of Birds and Reptiles. 

 Moreover there is a considerable number of Sharks and 

 Rays in which not only are the ova fecundated inter- 

 nally but the embryos also complete their development 

 within the body of the parent, much as in the manner 

 of Mammals. 



In the first case (external fertilization) the eggs are 

 small and shell-less and the embryo, of course, deve- 

 lopes, from first to last, quite independently of the 

 parent. The series of preparations in Case 12 illus- 

 trates the developmental history of the common Salmon 

 from the egg to the free-swimming larva. 



In the Stickleback (of which a pair with nest and eggs are shown in 

 Case 12) the male builds a nest in which he induces certain females to lay 

 their eggs, and these eggs he guards jealously until they are hatched. 



In the Sea-horse (of which a brooding male with the nursing-pouch laid 

 open is shown in Case 12) the male has an abdominal pouch into which the 

 eggs are received and in which they remain until development is complete 

 and larval growth well advanced. 



And there are several other species of fishes in which one of the parents, 

 usually the male, watches over the developing offspring. 



Where impregnation is internal, as among the Sharks 

 and Rays, the eggs are large, and they may either be 

 encased in a tough leathery shell, or they may be shell- 

 less : in the latter case they are not laid as eggs, but 

 undergo development within the oviduct, so that the 

 young are born alive. 



In Case 12 the eggs and development of two species 

 of Dog-fish are exhibited : the eggs are enclosed in a 

 curious shell and are hatched quite independently of the 

 mother. 



In the same Case (12) is shown a specimen of the 

 unborn young of a Hammerhead Shark. Here the 

 5 



