OBSERVATIONS ON INSTANTANEOUS 



CHANGES IN COLOR AMONG 



TROPICAL EISHES. 



Br CHARLES H. TOWNSEND. 



NEARLY all the tropical fishes on exhibition in the New 

 York Aquarium have the capacity of instantaneous changes 

 in color according- to their moods or artificial excitements, and 

 their many phases of coloration and markings have become more 

 noticeable under recently improved conditions of management. 



Since July, igo8, sea fishes in the Aquarium have been kept 

 in pure sea water supplied from a reservoir containing 100,000 

 gallons, the use of the brackish and impure water of the harbor 

 having been abandoned, except in certain verv large pools. The 

 temperature and salinity of the water approximate those to which 

 the fishes are accustomed in nature. 



The glass-fronted exhibition tanks, some of which are eight 

 feet long, are lined with artificial rockwork, and have the bot- 

 toms covered with sand or gravel, all of which assists in making 

 the conditions of captivity decidedly favorable. The fishes spend 

 much time resting among the rock crevices or on the white sand 

 below. 



The various species of fishes from the Bermuda Islands are 

 now maintained in better condition than ever before, and most 

 of them have adapted themselves to captivity, feeding, playing 

 or fightinr in apparently natural ways. 



It is well known that sea fishes habitually frequenting green or 

 yellow seaweed acquire and maintain the general color tone of 

 their habitat, and that trout from dark water are dark colored, 

 while those inhabiting waters where there is sandy or gravelly 

 l)ottom are light colored. 



Such conditions have long been appreciated at the Xew York 

 Aquarium, where fishes kept in tanks lined with white tiles, ha- 

 bituallv wear their lighter colors, only an occasional blind fish 

 remaining unchanged. The pale, colorless blind fishes of the 

 Mammoth Cave gradually become darker when exposed to light 

 in the Aquarium. These fishes, although with eyes practically 

 useless, are still able to distinguish light from darkness. A speci- 

 men from Mammoth Cave which has lived in the New York 

 Aquarium three years has gradually become quite dark. 



