no SALT-WATER FISHES 



with the habit of digging up crustaceans or flat-fish from the 

 sand. The torpedo is, however, a sluggish fish, and has 

 other resources in the pursuit of its prey, for it doubtless lies 

 in ambush and numbs any fish that may come in contact 

 with its disc. Its eye has the same sensitiveness as that of 

 all the rays ; and Mr. Bateson, who some time ago conducted 

 some very interesting investigations on the sense-organs of 

 fishes, has recorded* that the pupil of the torpedo's eye is 

 circular by night, but that by day the lower limb of the iris 

 comes up over it so as to leave only a horizontal slit. In 

 the common skate, on the other hand, it is a descending 

 shutter which protects the pupil in the daylight, and this is 

 drawn away when darkness falls upon the waters. Mr. 

 Bateson was able to demonstrate these wonderful arrange- 

 ments with the aid of a flash-lantern, which he suddenly 

 turned on the fishes in the aquarium tanks at night. The 

 practical aim of his enquiry, it should perhaps be mentioned 

 for the benefit of those who think that such an institution 

 justifies its existence only as long as it is " sternly practical," 

 was connected with the all-important bait question, it being 

 very necessary to ascertain which fishes find their food by 

 scent, and which, on the other hand, trust to sight. The rays 

 he assigned to the former category, and with them the sole ; 

 all the rest of our important food-fishes he regarded as 

 hunting by sight. 



The torpedo does not grow to a great weight, though 

 an example of 82 lb. weight is on record, and it occurs on 

 most parts of our coasts. It may easily be recognised by 

 the rounded head. Its colour, however, is no sure guide, 

 for both the ground shade and the spots vary in almost 

 every two specimens. That it procures its food with the 

 aid of its fibrous, disc-like, muscular electric organs and 

 swallows its victims whole is obvious from the poverty of 

 its teeth and the fact of fish as large as 5-lb. salmon having 

 * Journal of the Marine Biological Association, April, i8qo. 



