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J. S. NICHOLAS 



uncut earthworms will stimulate Ameiurus by slime secreted 

 by the skin. This is not the case in A. tigrinum, a fact which may 

 indicate that the probable sensitivity of combined air and water 

 breathers is not so great as single smellers. Red rubber tubing 

 of small diameter was used to simulate earthworms. Uncut 

 earthworms were allowed to move about in the half of the aqua- 

 rium not containing the Amblystoma. The rubber tubing was 

 more effective in eliciting a response if set in motion by means of 



TABLE 2 

 Diffusing substances 



TABLE 3 



Non-diffusing substances 



a cotton thread. Both objects acted solely as visual stimuh, 

 as can be seen from the accompanying table (table 3) . 



8. Experiments with odor streams 



Risser has described an apparatus with which he tested the ol- 

 factory reactions of the toad. The apparatus consisted of a test- 

 ing chamber into which odors were brought from an odor chamber 

 by means of an air current. 



A modification of this method was devised. The source of 

 the air current was a compressed-air system, the air being run 



