ANIMAL BEHAVIOR. 30 



T 



An object must be in motion in order to excite attention, and 

 it is not generally the moving form that is directly perceived, 

 but the movements of the water, travelling from the object to 

 the sensory hairs, are felt, and in such a way as to give the 

 direction of the disturbing centre with most surprising accu- 

 racy. If a bit of beef is taken up adhering to the point of a 

 needle, and held in the water, the vibrations imparted to the 

 needle by the most steady hand will be sufficient to give the 

 animal the direction. If the meat falls to the bottom, and 

 the needle is held in place, the animal approaches the needle 

 and tries to capture it, without paying the slightest attention to 

 the meat lying directly below. If, after the meat has fallen, the 

 needle is withdrawn and touched to the surface of the water 

 behind or at one side of Necturns, it turns instantly in the 

 direction of the needle, not because it sees, but because it feels 

 wave motions coming from that direction. Long experience 

 with Nectunts and with many of its nearer allies enables me to 

 speak very positively on this point. When it is remembered 

 that in the higher animals the direction of sound waves is given 

 by the auditory sense organs, which are primarily surface sen- 

 sillae homologous with those in the skin of Nectunts, it may 

 not seem so strange that the animal directs its movements in 

 the way described. Necturiis can see, but it can feel (perhaps 

 we should say hear) so much more efficiently that its small 

 eyes seem almost superfluous.^ 



1 Professor Eigenmann has kindly written the following note on the use of the 

 tactile organs in the blind fishes : 



Chologaster fapilliifrrus, a relative of the blind fishes living in springs, de- 

 tects its prey by its tactile organs, not by its eyes. A crustacean may be crawl- 

 ing in plain view withoiit exciting any interest unless it comes in close proximity 

 to the head of the fish, when it is located with precision and secured. The action 

 is in very strong contrast to that of a sunfish, which depends on its eyes to 

 locate its prey. A Gammarics seen swimming rapidly through the water and 

 approaching a Chologaster from behind and below was captured by an instanta- 

 neous movement of the Chologaster, when it came in contact with its head. The 

 motion brought the head of the Chologaster in contact with the stem of a leaf, 

 and instantly it tried to capture this also. Since the aquarium was well lighted, 

 the leaf in plain sight, it must have been seen and avoided if the sense of sight 

 and not that of touch were depended upon. 



In Amblyopsis, the largest of the blind fishes of the American caves, the bat- 

 teries of tactile organs form ridges projecting beyond the general surface of the 



