56 RALPH EDWARD SHELDON 



larly grassy or uneven spots. The head is moved rapidly from 

 side to side as the fish swims slowly, coursing in gradually dimin- 

 ishing circles, two or three inches from the bottom. When within 

 two or three inches of the crab the dogfish seizes it suddenly, mak- 

 ing off in a swift rush. As remarked by Field, the crab is shaken 

 violently from side to side for a moment, as the shell is crunched 

 and broken by the powerful jaws of the fish, after which it is 

 quickly swallowed. Occasionally, however, the crab is dropped 

 during the process. When this occurs a search, similar to the 

 first, follows until it is found again. 



At no time did the dogfishes appear to make any use of the sense 

 of sight in feeding. A crab hidden in eel grass is found as quickly 

 as one lying on the open bottom; moreover, one is found equally 

 quickly whether lying in its venter, exposing the dark carapace, 

 or on its dorsum, with the light colored venter showing conspic- 

 uously. A dogfish, dropping a crab, is apparently absolutely 

 unable to find it again excepting by means of the same sense 

 which enabled recognition of food in the first place. It was ob- 

 served, however, that a dogfish with food is usually followed by 

 otheis in the vicinity, which endeavour to secure possession of 

 it. Moreover, the fish will frequent for some time thereafter 

 the region of the pool in which food was found. This is probably 

 due to olfactory stimuli, although sight may be brought into play 

 to a slight extent. It was often noted that a dogfish would circle 

 around the spot where a crab had lain, often biting into the bot- 

 tom at the exact spot; probably some bod}^ juices had escaped 

 into the ground. Now and then a crab was placed on the bot- 

 tom near the screen separating the experimental from the lai'ger 

 pool. If no fishes, capable of finding food, were present in the 

 former, it would often happen in a few minutes that eight or ten 

 dogfish from the large pool would be swimming rapidly back and 

 forth along the screen, endeavoring to find their way through. 



Some experiments were tried with a hook and line baited with 

 the flesh of a rock crab tied in cheese cloth. The dogfish here 

 followed the same procedure as when the crab lay on the bottom. 

 On noting the proximity of food the fish begin to swim, as before, 

 in circles but, for a time, persistently search the bottom beneath 



