NOTES ON SOME PROBLEMS OF ADAPTATION. 99 



ously enough, in his review fails to mention the significant 

 occurrence of Ogilbia at Bermuda -other species occur (0. 

 ventralis) "in rocky pools about the Gulf of California and at 

 La Paz," and (Brosmophycis cayorum) "on a shoal covered with 

 algae at Key West." My own specimens of 0. verrillii, obtained 

 singly and at scattered intervals, were secured from widely 

 separated points about Bermuda -along the shore of Flatts 

 Inlet, on the north side of Dyer Island, in Fairyland Creek, and 

 in Tucker's Town Bay. In each case the habitat was at about 

 low water level, either under a rock of some size or else in a 

 dense mass of reddish and brown algae. The length of these 

 individuals was not over 4.5 cms. In color they were brownish 

 yellow, speckled with minute red dots; there was little indica- 

 tion of counter-shading. They are not vigorous swimmers. 

 When exposed to bright sunlight, by the sudden overturning of 

 a rock slab, they seemed stupefied, and in several instances were 

 easily secured by hand. 



I wished to examine the behavior of these fishes toward light, 

 and although but six specimens were available for experimenta- 

 tion, at different times from April, 1916, to December, 1917, the 

 observations made seem adequate for certain purposes. 



These fishes were intensely reactive to sunlight. If placed in 

 an aquarium with one end illuminated from above, they remained 

 almost stationary in the shaded portion, and if caused to swim 

 toward the lighted area they turned back almost instantly when 

 the anterior end came into the light. With direct sunlight, 

 temperature 26 C., the reaction time averaged 1.3 seconds. 

 Rheotactic response was also well marked, the animals heading 

 in the usual way into a current. Taking advantage of this 

 response, by appropriately directing a mild stream of water into 

 a circular dish, it was possible to induce swimming movements 

 without touching the fish. 



Stimulated in this way, an Ogilbia would swim slow T ly up to 

 the edge of a sharply defined sunbeam and remain stationary in 

 the shade. Comparatively violent, undirected, swimming could 

 be induced by suddenly illuminating the whole dish. Swimming 

 movements ceased almost immediately when the light was 



