54 POPULAR SCIENCE MONTHLY. 



papilliferus most of the ridges are much less prominent than in 

 the blind species, being sunk into the skin. About the nose and 

 chin, however, the ridges are as prominent as in the other species. 

 In the small Chologaster cornutus there are no distinct ridges 

 at all, the tactile organs being arranged 

 as in other species of fishes. In speci- 

 mens 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 papilla? 

 become prominent. The number of 

 individual papillae in each tactile ridge 

 differs considerably with age (size), so 

 that an exact comparison between the 



Fig. 6. — Snout of Choloijuster pupil- , » 1 l • i j_i i n 



lifer us, to show the tactile ridges. 1 arge Ambly opsis and the much smaller 

 species of Chologaster and Typhlich- 

 thys can not be made. From a number of counts made by Pro- 

 fessor Cox I take the liberty of giving the following: Ridge No. 

 6 contains, in Chologaster papilliferus, six organs; in Typhlichthys, 

 eleven; in two specimens of Amblyopsis, respectively eighty-three 

 and one hundred and six inches long, twelve and twenty. 



Aside from the tactile organs in ridges, there are many soli- 

 tary ones not evident from the surface in Amblyopsis. When 

 the epidermis is removed by maceration, the dermal papillae on 

 which these rest give the whole head a velvety appearance. 



In the young, at least of Amblyopsis, each of the tactile organ 

 of the ridges is provided with a club-shaped filament abruptly 

 pointed near the end. They wave about with the slightest motion 

 in water, and are so numerous as to give the whole head a woolly 

 appearance. 



To recapitulate the facts ascertained concerning the eye and 

 tactile organs: 



1. The eyes were degenerating and the tactile organs develop- 

 ing beyond the normal before the permanent underground exist- 

 ence began. 



2. The eyes continued to degenerate and the tactile organs to 

 increase after permanent entrance to underground waters. 



3. In the degeneration of the eye the retina leads; the vitre- 

 ous body and lens follow; the more passive pigmented layer and 

 sclera remain longest; the bony orbit is not affected. 



Bearing of the Facts gained on the Origin of the Cave 

 Fauna. — The origin of the cave fauna and of the blind fauna 

 are two distinct questions. This was first recognized by Ii. 

 Garman. Before, the two questions were considered as one, 



