26 CHARLES F. W. McCLURE 



larval and adult anura; by the simple method of immersing only 

 a portion of the body of the larva or adult in the acid dye solution, 

 and by feeding experiments on adults. 



A. Suspension of only a portion of the body in a solution of colloidal 



acid dye 



It was found that neither larvae nor adults endure a prolonged 

 and continuous treatment of this character. It was therefore 

 found necessary to subject them at intervals to a number of short 

 immersions, after which they were immediately transferred to 

 aquaria. The amount of dye which enters the body in such cases 

 is naturally limited, and this method does not indicate the extent 

 to which the tissues might have stored the dye within the time 

 limits of the experiment if the suspension in dye had been 

 continuous. 



Every precaution was taken to prevent the possibility of any 

 dye reaching the alimentary canal through the oral cavity. The 

 tails of the smaller larvae were suspended in the dye through the 

 meshes of a mosquito netting, while brass funnels were used for 

 the larger larvae of II . catesbiana. Adult frogs and toads were 

 bound to glass rods with wide-meshed bandages. This makes it 

 possible to suspend the legs and body in the dye to the extent 

 desired. The pressure of the bandage on the body undoubtedly 

 obstructs the lymph flow to some extent, but this is unavoidable. 

 In the case of all adult frogs and toads, from twelve to twenty- 

 four hours were allowed to elapse between the time of the last 

 suspension in dye and the time of killing. 



Experiment 10. (Partial immersion of young larvae in solutions 

 of low concentration). 



a) The tail of a larva of R. sylvatica was suspended for fifteen 

 minutes on May 11 in a 1:1000 solution of trypan blue and the 

 larva then transferred to tap water for twenty-four hours before 

 killing. A study of serial sections showed that no dye had been 

 stored in any tissue of the body. 



6) The tail of a larva of R. sylvatica was suspended for about 

 fifteen minutes on May 11 and 12 in a 1 : 1000 solution of trypan 



