BEHAVIOR OF ANURA TOWARD COLLOIDAL DYES 21 



It is difficult matter to lay down a rule which would answer in 

 all cases, regarding the shortest time required for dye to be stored 

 in all of the typical tissues. It may be stated, however, in such 

 advanced larvae as those mentioned above, that dye granules 

 will usually be found in many of the typical tissues, after twenty- 

 four hours immersion in dye (1 : 1000) and twenty-four hours in tap 

 water before killing. As a guide to those who wish to repeat the 

 experiment, forty-eight hours is the lowest average limit I would 

 care to assign in the circumstances, as considerable individual 

 variation is met with. This is well shown on table 6 which 

 illustrates the variable length of time required in different indi- 

 viduals for the lymphatics of the caudal fin to store the dye. The 

 extent to which dye has been stored in the caudal fin lymphatics 

 may be regarded, in general, as an index of the relative extent of 

 its storage in other typical tissues. Cases in which no dye has 

 been stored in the caudal fin lymphatics do not necessarily signify, 

 however, that it may not have been stored elsewhere in the body. 

 See Experiment 7 b. 



In larvae of R. temporaria which had been placed in solutions 

 of trypan blue (1 : 800-1 : 1600) at time of hatching, Wislocki ('16) 

 observed on about the fourth day of immersion faintly discernible 

 traces of dye to be present in the lymphatics of the caudal fin. 

 On the eighth day of immersion he found all of the lymphatics of 

 the fin to be deeply stained. 



In may be of interest to compare the above observations of 

 Wislocki with those of the writer found on table 6. 



All of the above-mentioned experiments have thus far been 

 made upon relatively young larvae. The two following experi- 

 ments (Experiments 8 and 9) show that the method of vitally 

 staining typical tissues by immersing young larvae in solutions of 

 acid dyes, can also be applied to year-old larvae of R. catesbiana 

 and to adult anura. 



