FEEDING HABITS OF AMBLYOPSIS. 



83 



robin (Prionotus carolinus), according to Morrill and Herrick, finds its food largely by sight and by 

 the use of the free pectoral fin-rays which are tactile in function. The king-fish (Mentkirrhus 

 saxatUis) uses sight somewhat, but in the main the tactile organs are used as most of the food was 

 taken by contact, and non-nutritious substances were generally taken. The toad-fish (Opsanus 

 an) did not find concealed bait and seemed to get its food wholly by the visual and tactile senses. 



Herrick concludes from his experiments that fishes which possess terminal buds in the outer 

 skin taste by means of these organs and habitually find their food by their use. Fishes which lack 

 these organs in the skin have the sense of taste confined to the mouth. The delicacy of the sense of 

 taste in different parts is directly proportional to the number of terminal buds in these areas. 



Amblvopsis has terminal buds scattered over the entire head. They are most numerous on the 

 lips and the tip of the snout. I did not determine whether or not they were present on other parts 

 of the body. My experiments indicate that, if they are present on parts other than the head, they 

 are but few in number. While these fishes are without doubt able to taste with the buds on the 

 lips and snout, practically all of their food is found by means of the tactile sense. I am unable to 

 say how the terminal buds compare in number with those of other fishes. The young fishes up to 

 20 mm. in length do not have terminal buds developed. Since this is the case they have only the 

 tactile sense for finding food, for smell plays only a minor part, if any. 



Ritter says that in Typhlogobius the tactile sense has not only not increased, but has actually 

 diminished pan passu with the diminution of the power of sight. Such is certainly not the case in 

 Amblyopsis. Eigenmann says : 



"(i) The eyes were degenerating and the tactile organs developing beyond the normal before 

 the permanent underground existence began. 



"(2) The eyes continued to degenerate and the tactile organs to increase after the permanent 

 entrance to underground waters." 



The tactile organs are arranged in rows or ridges. An examination of the number of individual 

 tactile organs in the same 3 ridges in each of 8 fishes gives the following counts: 



Whether the individual tactile organ is more highly developed in the adults than in the young 

 would be difficult to say. At any rate the above figures show that in the adults tactile organs are 

 much more numerous than they are in the young. 



Since, in the blind fishes, the factor of sight is entirely eliminated, we have left the senses of 

 taste, touch, and smell by which they may find their food. In testing which of these is concerned 

 I used about 50 individuals. My best results were obtained by placing the fishes in battery jars 

 (one in each jar) 7 inches in diameter and 8 inches high. The water in these jars was from 4 to 

 5 inches in depth. This enabled me to eliminate all factors except those which I introduced. 



During the summer of 1906 I kept a number of fishes in an aquarium in the cave. I tried to get 

 them to eat meat, but had no success. In September of the same year, I transferred other fishes 

 to the laboratory at Bloomington, where my experiments were made. Some individuals begin to 

 eat in a few days, others not till several weeks after they are confined. The young, from 25 to 40 

 mm. in length, and the adults seem to become adjusted to their new conditions much more readily 

 than those about half-grown. Those from 60 to 70 mm. in length are much more sensitive to me- 

 chanical stimuli than either the young or adults, and further their sense of fear seems more highly 

 developed at this time. 



When first brought into the laboratory, I kept the fishes in a dark room so as to have the con- 

 ditions as nearly normal as possible. As this necessitated a light while making the observations, 

 I abandoned it for a lighted room, but several observations were made in the dark room, where 

 I often tried to feed them meat from the end of a thread. After 4 weeks, I got some of the larger 

 ones to take a few pieces, and one large fish took 5 pieces in as many minutes. The next day I 

 found the meat lying on the bottom of the aquarium. In no case did I get the fishes to take meat 



