58 MADRAS FISHERIES BULLETIN VOL. XIV, 



Fisheries, for the two-fold reason that this department has parti- 

 cular need for aquarium facilities in the carrying on of its investi- 

 gations of the life-histories of our local food fishes and because of 

 the greater facilities it has for stocking and supervision. One 

 outcome of the department's activities is the present descriptive 

 guide; another is the installation of electric lighting and fans. 

 That the improvements effected have been appreciated is proved 

 by the great increase in the number of visitors who have paid for 

 admission ; in 1918-19 the total was 96,957 only, in 1919 20 it rose 

 to 16.^517. 



On entering the main hall, five large tanks are seen on either 



side ; a central floor pond for fresh-water animals and a number of 



table aquaria complete the accommodation available for the fishes 



and other animals on view. The aeration of the water in the tanks 



is dual, partly by the inflow of filtered sea-water from a high level 



reservoir, partly by means of an air compressor delivering air 



in a mist of tiny bubbles at the bottom of each tank. To obtain 



sufficiently minute division of the air stream, it is delivered 



under pressure through a filter candle hung in the tank. By this 



means the water is kept so well aerated that it is possible to 



maintain a permanent state of overcrowding seldom found except 



temporarily in the open sea. Unfortunately it is impossible to 



regulate this super-aeration to suit the varying constitutional 



susceptibilities of every kind of fish. Some suffer in consequence 



from a disease we may call " gas-eye." It arises from an excess of 



air finding its way into the blood stream, by absorption through 



the gill membranes; the outward sign of the disease is the partial 



protrusion of the eyeball. Some fish thus affected eventually 



recover, and all do so quickly if transferred to ordinary sea-water. 



The majority if left in the tanks and unmolested sicken and die, 



the actual cause of death being asphyxiation. But usually the 



sight of a protruding eyeball is the signal for an onslaught by its 



companions, particularly of certain species, who begin by viciously 



tearing out the offending eye and end by killing the victim if they 



can possibly manage it. Animal life in the sea has noplace in its 



economy for hospitals and panjrapoles. As a consequence one 



never meets a cripple and very seldom a diseased animal in the 



sea ; life there is for the healthy and the strong alone. 



The recent installation of electric light enables the tanks to be 

 brilliantly illuminated after dark ; it is an improvement that has 



