OLFACTORY REACTIONS IN AMPHIBIANS 623 



nate between earthworms and dungworms. The latter were 

 irritated in such a manner as to make the integumentary exudate 

 distinctly noticeable. This was not deterrent in any case. 



Whatever may have been the cause of the refusal of the 

 dungworms in the earlier trials has not been made clear, for 

 later trials showed no aversion to the dungworms on the part of 

 the toads. 



A series of trials with the toads, in which the conditions of 

 feeding were carried to a degree far beyond what might be 

 expected to occur at any time normally, showed that many odors 

 were not repellent when associated with food. 



To hungry toads was given the choice of taking mealworms 

 with unknown odorous substances, and others without such 

 substances. Ether, chloroform and alcohol could not be made 

 use of, because of their fatal action on the mealworms. Clove 

 oil, oil of cedar, oil of pennyroyal, oil of bergamot, oil of cit- 

 ronelle, aniline oil, carbon bisulphide and iodine in saturated 

 solutions were made use of. In the experiments there often 

 arose the question of a fatal dose. But none of the toads died 

 during the trials. Several of the trial records are transcribed : 



Toad No. 1. One mealworm eaten, after which two meal- 

 worms with oil of pennyroyal taken within one minute; only 

 effect was 'gaping' several times. Rest for ten minutes, then 

 mealworms put in a dish too high for toad to get into. Toad 

 in attentive attitude, and again when offered took clean worms 

 and also one with oil of cloves. Odor was not repellent, nor 

 was any after-effect noticed. 



Four days later the same toad ate three mealworms, two with 

 clove oil and one with oil of citronelle. 



Toad No. 3. Took in two successive trials, two clean meal- 

 worms, two with oil of pennyroyal and two with carbon bi- 

 sulphide; and later two clean mealworms, two with aniline oil, 

 and two with oil of rose geranium. 



Toad N'o. 5. At one trial, took two mealworms with oil 

 of pennyroyal and one earthworm with the same oil applied. 



The oil of pennyroyal appeared to be more irritating to the 

 lips of the toads than the other substances used; the wiping 



