G. NATUKAL HISTORY AND ZOOLOGY. 313 



The development appears to be exceedingly rapid. In two 

 days after the ova were first seen in the tank, not only was 

 the form of the fish discernible in many of them, but the 

 young fry, just hatched, were detected in the water enjoying 

 independent life. They were about three sixteenths of an 

 inch in length when first hatched out. 2 A, Dec. 6, 1873, 565. 



EGGS OF THE SILUEID^E. 



It is an interesting fact in the economy of certain fishes, 

 especially of those belonging to the family of the Siluridw, 

 that the mouth constitutes the nest for hatching the eggs, 

 these to the very limited number of from five to twenty be- 

 ing kept in this cavity, usually that of the male, until they 

 are hatched. They are probably caught up after exclusion 

 and fertilization, and retained. Some of these eggs are half 

 an inch in diameter. The fact of this peculiarity in the case 

 of the genus Arius and some of its allies in America has long 

 been known ; and Dr. Day announces the same condition in 

 certain Indian species of Arius and Osteogeniosus. 12 A 9 

 February 5, 1874, 272. 



SENSIBILITY OF FISH TO POISONS. 



It has been the prevailing impression that fishes are less 

 liable to the influence of poisons than the other vertebrates ; 

 but this is shown to be incorrect by a series of experiments 

 lately prosecuted by Rabuteau and Papillon in the laborato- 

 ry of Concarneau. In one case, some small fishes, such as 

 eels, rays, sea-horses, etc., weighing from one hundred and 

 fifty to five hundred grains each, were placed together in a 

 quart of sea-water in which were dissolved two and a half 

 centigrammes of strychnine. At the end of four hours all 

 were dead, with the usual symptoms of strychnine poisoning. 

 The convulsions were most appreciable in the flat-fish and in 

 the rays. 



Some very curious experiments were made in the way of 

 hypodermic injections of strychnine in certain rays ; and the 

 authors recommend the very young of this species as emi- 

 nently suited for watching the progress and symptoms of 

 poisoning, since the skin of the belly is so transparent as to 

 permit all the changes which occur in the lungs, heart, and 



the larger vessels to be observed without difficulty. Experi- 



O 



