Sheldon, Reactions i(j Cluvinrnl Sfi/niili. 279 



sl.iniulus. This is evidently the beginning of n, swimming movement. 

 Stimnhition of the anns results usually in bending over ventrad of the 

 pelvic fins. Occasionally the fins react alternately in an attempt to 

 turn the body over. If the. stimulus is strong or long continued, 

 these reactions are followed by a lateral squirming of this part of the 

 fish culminating in the swimming away of the animal. Stimulation 

 of the claspers results in a (juick lateral movement and vibration of 

 the structures. The head responds by a rather slow movement away 

 from the solution. In general, stimulation of the dorsal, lateral, and 

 ventral surfaces, other than those already mentioned, results in a 

 movement of the fish which is very evidently a part of the general 

 swimming movement. In fact, stimulus of almost any region of the 

 fins or body, if persisted in, will transfer the local reaction to one 

 which forms jiart of the swimming movement of the animal. This 

 is shown especially in the case of stimulation of the fins or lateral 

 surfaces. If the caudal, second dorsal, or anal fin is stimulated and 

 the reaction is toward the stimulus, for instance, there will often be 

 a movement of the first dorsal fin but in the opposite direction. The 

 same relation holds true if the first dorsal fin is stimulated. Often 

 a reaction of all the fins is secured. For example, there will be a 

 movement toward the stimulus by the caudal, anal, and second dorsal 

 fins, a movement away from the stimulated side by the first dorsal 

 fin, an u])ward movement of the jiaired fins on the side stimulated 

 and a downward movement on the opposite side. This reaction was 

 first pointed out to me by Dr. Parker as a response secured by tactile 

 stimulation of the same regions. Such reactions are unquestionably 

 part of the general swimming movements of the fish, as may be seen 

 by observing the animal in an aquarium. As caused by chemical 

 stimuli, they are evidently of a kind to preserve the fish from injury, 

 enabling it to remove itself from an injurious environment. Very 

 similar reactions are secured by stimulation of the sides of the body 

 and tail. In general it can be said that a slight stimulus calls forth 

 a local response, while a stronger or longer-continued stimulus almost 

 invariably results either in a new reaction which is part of the swim- 

 ming movement, or else in a gradual change of the local reaction into 

 such a part of the swimming movement. The former occurs where 



