28o Journal of Comparative Neurology and Psychology. 



the local reaction differs decidedly from the swimming movements, 

 as in the case of stimulation of the moutli, while the latter holds in 

 cases where the two are similar, as in the reactions due to stimula- 

 tion of the tins. Certain interesting special cases are to he noted. If 

 the dorsum or side of the fish near the small iinlets of the dorsal or 

 anal fins be stimnlated, a, quick movement of the finlets toward the 

 side stimulated, usually followed by vibration of the finlet, occurs. 

 This may be a reaction to remove an irritant, as is noted in the case 

 of the frog when a droj) of acetic acid is placed on the skin, or it may 

 be i^art of the swinuning movement, as seems more probable. Evi- 

 dence against the former interpretation is ottered by resnlts which 

 Parker obtained by tactile stimulation. He found that tactile stimu- 

 lation of the dorsum near the fiidet of the second dorsal fin caused 

 this reaction ; but he also found that if he now stimulated a point be- 

 tween the finlet and the mid-dorsal line on the same side the finlet 

 continued to wipe the skin, but ventrad of the point now stimulated. 

 It would, therefore, appear that the reaction is called forth by stimu- 

 lation of any part of the side in this region and is not a local response 

 to remove an irritant. It might be argued, however, that the power 

 of localization is not well developed in this form. The strongest evi- 

 dence in favor of the second interpretation is that when the skin be- 

 side both dorsal finlets is stimulated on the same side at the same time 

 one turns to one side and one to another, as is the case when the 

 aninml is swinuning. This reaction of the finlets was one of the most 

 delicate found. Reactions could be secured by stinuilation of the skin 

 beside the second dorsal finlet when all the remainder of the body was 

 insensitive. 



If the claspers are turned to one side and the venter underneath 

 stimulated, a quick vibration of the claspers over this point follows. 

 This is i^robably })art of the general swimming movement also, al- 

 though its constancy and accuracy suggest the wiping reaction. In 

 the case of the pectorals, however, when the ventral surface between 

 them is stimulated there follows a quick scissors-like action of the two 

 fins over the point stimulated. If one fin is held, the reaction takes 

 place with the other alone. This reaction is not a part of the general 

 swimming movement, is very consistent and accurate, and apparently 

 is of the same character as the wiping reaction of the frog. It is 



