IOO W. J. CROZIER. 



obstructed. Ogilbia is very strongly thigmotactic and in most 

 cases settled in the angle between the bottom and the wall of an 

 aquarium. 



With two specimens it was possible to remove the eyes and to 

 keep the animal alive for about 24 hours thereafter. The eyes 

 are quite small (Fig. i) and burning operations were unsuccessful, 

 two fishes being killed in attempts to obliterate the eyes in this 

 way. The eyeless fishes were also found to be sensitive to light, 

 and to orient, with some precision, away from it. The reaction 

 time to direct sunlight was, in the one case measured, about 3 

 seconds. 



Even with normal specimens, it was possible to induce weak 

 swimming by illuminating merely the hinder half of the body. 



There seems consequently no reason to doubt the occurrence 

 in Ogilbia of a true photic sensitivity of the skin -a result of 

 special significance in view of the integumentary photic sensitivity 

 found in Amblyopsis (Payne, '07), and of the fact that the blind 

 Cuban brotulid Lucifuga (Eigenmann, '09, p. 199) seems probably 

 to be photonegative (although the data are scanty). This type 

 of irritability is rather characteristic of cave vertebrates, and its 

 presence in Ogilbia is perhaps susceptible of a significant inter- 

 pretation. In Eigenmann's view, the blind cave fishes derive 

 from types originally photonegative, living in darkness under 

 stones along "coral" reef shores, which survived a process of 

 adaptive adjustment to fresh water and to cave environments 

 conditioned by gradual elevation of the land. 2 It is frequently 

 assumed that special modes of behavior, notably those dependent 

 upon enhanced photic and tactile irritability, represent new 

 developments determined in relation to blindness and to the 

 conditions of cave environments. Hence it is important to 

 recognize that even a manifestation so rare among marine fishes 

 as skin sensitivity to light, is adequately exemplified in a teleost, 

 not cave-inhabiting, but with eyes seemingly degenerate and on 

 other grounds assigned as representative of the ancestral origin 

 of typically adjusted cave forms. The state of pre-adaptation 



2 It may be mentioned that I have several times made search for fishes in cave 

 pools at Bermuda, but have never encountered fishes in them, save where obvious 

 communications led to outside water. 



