PHYSIOLOGICAL EFFECTS 121 



Unlike animals are able to protect each other 

 in this respect apparently as effectively as simi- 

 lar forms. Water in which fresh- water mussels 

 have lived and into which they have secreted 

 slime will protect fishes and other animals from 

 the harmful action of some poison as effectively as 

 will the presence of other fishes. 



The physiological effects of groups of fishes 

 even in non-schooling species do not end with 

 respiration and survival effects. Experiments 

 have shown that four goldfishes will learn a simple 

 maze more rapidly than will isolated fishes. The 

 experiment is run in this way. A series of small 

 glass-sided aquaria are set up each of which con- 

 tains a heavy wire partition in the form of a cone 

 with the apex replaced by a sliding door. The 

 door is large enough for more than one fish to 

 swim through side by side. The fishes are placed 

 in the larger part of the aquarium with the cone- 

 shaped partition pointing toward the forward 

 and smaller end where the fishes are to be fed. 

 The fishes are trained to come through the door 

 in the funnel and be fed when a red light is 

 turned on. 



In some experiments eight fishes were placed 

 in such an aquarium, four were placed in two 

 others, two were put into four more and eight 

 more similar ones were isolated into eight addi- 



