﻿100 BLIND VERTEBRATES AND THEIR EYES. 



in which 6 blind fishes were swimming, where they had been for a number of days 

 undisturbed in a dark room, caused nearly all of them to dart rapidly forward. 

 A second tap produced a less unanimous reaction. This repeated on successive 

 days always brought responses from some of the inmates of the aquarium. Those 

 responding were not necessarily the nearest to the center of disturbance, but some- 

 times at the opposite side of the acjuarium or variously distributed through it. 

 After a few days the fishes took no notice of the tapping by any action observable 

 in the artificially lighted room. 



Such tapping on a well-lighted aquarium containing both Cholos^askr and 

 Amblyopsis was always perceived by the Amblyopsis, but the only response from 

 these imperturbable philosophers was a slight motion of the pectorals, a motion 

 that suggested that their balance had been disturbed and that the motion was a 

 rebalancing. The Cliologaster, on the other hand, invariably darted about in a 

 frantic manner. One individual of Amblyopsis floating on the water was repeat- 

 edly pushed down by the finger without being disturbed ; but if touched on the 

 side, they always rapidly dart away. 



From everything observed it is quite evident that Amblyopsis is not keener in 

 perceiving objects or vibrations than other fishes, and ordinarily pays much less 

 attention to them. Mr. Payne's observation on the feeding habits leads one to 

 conclude that they possess greater power of discrimination between vibrations. 

 Some observations on young Amblyopsis are of interest in this connection. 



The young with a large amount of yolk still attached show a well-developed 

 sense of direction. A needle thrust into the water near their heads and in front 

 of them causes a quick reaction, the young fishes turning and swimming in the 

 opposite direction. They will do this two or tliree times, then, becoming exhausted, 

 will remain at rest. Sometimes an individual will not move until it is actually 

 touched by the needle. The needle must come within about an eighth of an inch 

 of the fish before it is noticed. Then, if the needle produces any result, it causes the 

 fish to quickly turn and swim some distance, when the fish falls to the bottom again 

 and remains at rest. If the needle be placed behind the fish, it will swim directly 

 forward; if at the side or about the middle, it swims directly forward or turns and 

 swims in the direction opposite the origin of the disturbance. Younger specimens 

 have no power over the direction of their progress — the wiggling of the tail simply 

 produces a gyration, with the yolk as pivot. 



A young blind fish, 6 months old, swims about in a jerky manner, chiefly by 

 use of its pectoral fins. It keeps close to the side of the vessel, usually with its 

 back to the glass. (The aquarium was a cylindrical jar 300 mm. in diameter 

 and 300 mm. high.) From whatever direction it may be approached it perceives 

 a stick thrust toward it as readily as a seeing fish can, and will invariably dart 

 away a short distance, sometimes making sharp turns to avoid the stick and always 

 successfully. It can be approached from the to]) nearer than from the sides or from 

 in front. It does not avoid the sides of the atiuarium, which it frequently strikes. 



THE EAR OF AMBLYOPSIS. 



Anatomically considered, the ear of Amblyopsis is normal. Numbers of ears 

 together with the brains have been dissected out. These were treated with Flem- 

 ming's strong solution or with Hermann's fluid, either of which stained the nerve 

 matter black. In the first place, the three semicircular canals are present and 



