Spatially Determined Reactions 187 



against which, on the pressure theory, the fish should have 

 moved. Still more decisive was the experiment where young 

 fish were placed in a corked bottle full of water which was 

 submerged and put near a wall covered with algae. When the 

 bottle was moved in one direction, all the fish went to the 

 opposite end, although no current could have been produced. 

 Again, a wooden box with ends of wire netting, the bottom 

 covered with gravel and the sides with seaweed, was used; 

 fish (Fundulus) were placed in it, and the box was held 

 lengthwise in a strong current. The fish oriented them- 

 selves, but as soon as the box was released and allowed to 

 float away, they lost their orientation, though their relation 

 to the current was in no way altered. Blind fish, Lyon found, 

 oriented themselves by touch, sinking to the bottom. There 

 does, however, appear to be, in some cases, a genuine pres- 

 sure reaction to current, for when water is rushing through a 

 small hole into a tank containing blind fish, they keep their 

 heads to the current without touching anything. Here the 

 different parts of the stream have different velocity, and pres- 

 sure stimuli are actually applied to the skin. There must 

 be pressure reaction, also, when fish actually swim up-stream 

 instead of merely maintaining their places against a current 

 (155). Such a reaction was displayed, probably, by some 

 shrimps which, being in the water with the fish in the revolv- 

 ing tank experiment, did swim against the current instead of 

 with it (254). 



Some very interesting behavior touching on this same point 

 was observed by Garrey in a school of the little fish called 

 sticklebacks. He noted that if any object was moved along 

 the side of the aquarium containing them, the whole school 

 would move along a parallel line in the opposite direction. 

 If an individual fish happened to be heading directly toward 

 the object, it would turn in the opposite direction from the 



