BEHAVIOR OF ANURA TOWARD COLLOIDAL DYES 



11 



TABLE 4 

 Rana pipiens 



Experiment 4 (table 4). Forty-six (46) larvae of Rana pipiens, 

 measuring about 4.5 millimeters in length, were placed in a 1 : 2000 

 solution of trypan blue on April 11 and transferred to a 1:1000 

 solution on April 16. At the time they were first placed in the 

 dye solution the external gills had not made their appearance in 

 all of the larvae, so that the stage of development at time of 

 immersion was approximately similar to that of the toad larvae 

 in Experiment 1. As the frog larvae were brought into the labora- 

 tory at an early cleavage stage, the exact date of fertilization is 

 unknown, but probably occurred in the morning of April 7. 

 All of the larvae of this experiment were killed immediately on 

 removal from the dye solution, with the result that the dye in the 

 alimentary canal dissolved in the reagents and stained some of the 

 tissues diffusely. For this reason the tissues are not as favorable 

 for detailed study as those of larvae which have remained in tap 

 water twenty-four hours before killing. I have been compelled 

 to omit two other similar sets of experiments made on Rana on 

 account of my neglect to rid the alimentary -canal of dye before 

 killing and fixing the larvae. 



An examination of serial sections made of four (4) larvae of 

 Rana killed on April 12, six (6) killed on April 13, six (6) killed on 

 April 14, eight (8) killed on April 15, six (6) killed on April 16 and 

 six (6) killed on April 17, showed that no dye had been stored in 

 the cytoplasm of any cell in the body. 



