280 J. S. NICHOLAS 



4. When the animals are tested in darkness (table 1, series 

 3), the evident retardation in the time of reaction is due to the 

 dependence of the animal upon the sense of sight. 



5. After the removal of the eyes of the animals, they become 

 accustomed to use the olfactory organ only and in this way the 

 remaining sense organ is correlated to the needs of the animal. 



6. Experiments performed with diffusing and non-diffusing 

 substances (tables 2 and 3) demonstrate the fact that an animal 

 possessing the optic sense is stimulated by non-diffusing sub- 

 stances, while those possessing the olfactory sense are stimulated 

 by diffusing substances. 



7. Odor streams involving the use of a number of substances 

 (table 4) elicit no response on the part of the animal unless the 

 substance used possesses irritating properties, in which case the 

 animal responds by a decided motor reaction. 



8. Responses to motionless test substances in air (table 1, 

 series 3) show that the animal can find food substances, although 

 the reaction time is longer than if the animal and the test sub- 

 stance are submerged. 



9. The experiments indicate clearly that there is a definite 

 olfactory sense in both the larvae and the adults of Amblystoma 

 tigrinum. 



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 Arey, L. B. 1919 A retinal mechanism of efficient vision. Jour. Comp. Neur., 



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 Bruneb, H. L. 1914 a The mechanism of pulmonary respiration in amphibians 



with gill clefts. Morph. Jahrb., Bd. 48, S. 63-82. 



1914 b Jacobson's organ and the respiratory mechanism of amphib- 

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