THE TACTILE ORGANS. 



97 



as in the other species. In Chologaster cornutus there are no distinct ridges at all, 

 the tactile organs being arranged as in other species of fishes. In specimens of 

 the same size the papillae are not more prominent in papilliferus than in cornutus. 

 It is only in the oldest of papilliferus that the papillae become prominent. The 

 number of individual papillae in each tactile ridge differs considerably with age 

 (size), so that an exact comparison between the large Amblyopsis and the much 

 smaller species of Chologaster and Typhlichthys can not be made. From a num- 

 ber of counts, Professor Cox found that ridge No. 6 contains in Chologaster papilli- 

 ferus, 6 organs; in Typhlichthys, n ; in two specimens of Amblyopsis, respectively 

 3.33 and 4.25 inches long, 12 and 20. The tactile ridges in the head of Amblyopsis 



Fig. 3a. (a, 6, c) Distribution of Tactile Ridges in Amblyopsis; lateral, dorsal, and ventral views. 



(t/, e) Distribution of Tactile Ridges in Typhlichthys sublerraneus , dorsal and side views. 



are shown in plate 8, figures A and b. The outermost layer of skin has been re- 

 moved from a small area over the right eye of A, showing the numerous taste buds. 

 Figures c and D show head of Chologaster papilliferus under slightly greater mag- 

 nification. Figure D shows especially the tactile organs about the mouth. The 

 skin passes over the eye without a free orbital rim, and the eye does not show well. 



Aside from the tactile organs in ridges there are many solitary ones not evi- 

 dent from the surface in Amblyopsis. When the epidermis is removed by macera- 

 tion, the dermal papillae on which they rest give the whole head a velvety appearance. 



In the young, at least, of Amblyopsis, each of the tactile organs of the ridges is 

 provided with a club-shaped filament abruptly pointed at the end (fig. 31). They 

 wave about with the slightest motion in water and are so numerous as to give the 

 whole head a woolly appearance. 



