644 JONATHAN RISSER 



and second sets, but on account of the comparatively small num- 

 bers at hand, the results could not be considered as conclusive. 



With the material of the third set the chief aim was to deter- 

 mine whether the presence of the vaseline plugs was beyond 

 doubt inhibitive of the apparent olfactory reactions'. Some 

 operations of cutting the tract were carried out, but the after 

 effects were in most cases disastrous to the tadpoles, and there- 

 fore special stress was placed on plugging the nasal openings. 



Making use of the same individual tadpoles in the successive 

 trials, these groups were isolated in filtered water for some time 

 previous to each trial, and tested repeatedly for reactions to the 

 food as presented (without an envelope) while the nasal openings 

 were in normal condition, or when filled with the vaseline plug. 



The trials with the tadpoles in this series were carried out 

 in the following manner: The tadpoles were isolated in filtered 

 water for at least twenty-four hours, in a few cases forty-eight 

 hours, but not beyond this, as the tadpoles showed that a longer 

 period without food was disastrous to them. After isolation 

 for the designated length of time, the tadpoles were tested 

 for the presence of food in the water; immediately after this 

 the nasal plugs were put in, and the tadpoles transferred to a 

 vessel free of food or vaseline. The food was then introduced. 

 Unless the food mass was placed immediately in the proximity 

 to the tadpoles they exhibited no such activities as they pre- 

 viously had. "When swimming and moving about in the vessel, 

 there were no such positive attempts to' find the food as when 

 normal. The trials were repeated several times with different 

 groups of individuals, in each case allowing several days to in- 

 tervene between the trals, the tadpoles being provided with 

 food and water from the stock. 



The tadpoles showed no bad effects from the plugs of vase- 

 line in the na-al openings, reacting freely in the later trials as 

 well as in the earlier experiments. 



Tests made with the tadpoles having the plugs in the nares 

 showed them unable to discriminate between two packets one of 

 which contained food, while previous to the plugging definite 

 choice had been made by them in favor of the'food packet. 



