18 CHARLES F. W. McCLURE 



In larvae killed subsequent to June 12, dye granules were 

 invariably found. 



We know by experiment that the storage of dye granules by 

 certain typical tissues is generally potentially possible on the 

 ninth day after fertilization in Bufo. The circumstance that the 

 process has been prolonged in some of these larvae, appears to be 

 due not only to a difference in their degree of development at the 

 time of immersion, but also to the circumstance that conditions 

 at this tune are less favorable for the rapid ingestion or absorp- 

 tion of colloidal dye particles than at a more advanced age. 



If this view is correct it should be borne out by experiments on 

 more advanced larvae in which a storage of dye granules should 

 be accomplished within a still shorter time. 



6. EXPERIMENTS WHICH SHOW THAT THE STORAGE OF DYE GRAN- 

 ULES MAY BE ACCOMPLISHED IN A RELATIVELY SHORT TIME, 

 WHEN LARVAE ARE PLACED IN SOLUTIONS OF COLLOIDAL ACID 

 DYES AT AN ADVANCED STAGE OF DEVELOPMENT 



All of the larvae used in these experiments are so advanced in 

 development, that no doubt can exist that their tissues and organ 

 systems have attained a high state of differentiation. 



Experiment 6. (a) A number of toad larvae were placed in a 

 1 : 1500 solution of Niagara blue on August 16 (77 days after fer- 

 tilization). After twelve hours and fifteen minutes immersion in 

 the dye, some of the lymphatics of the caudal fin appeared to be 

 stained a light blue in one of the larvae. An examination of the 

 living larva showed that dye granules were beginning to be 

 stored in the cytoplasm of the lymphatic endothelial cells. The 

 liver and mesonephros were immediately removed from the body 

 and sectioned. No dye granules were observed in the cytoplasm 

 of the stellate cells of the liver, or in the epithelium of the meso- 

 nephric tubules. A few mononuclears containing dye granules 

 were found, however, in the capillaries of the liver and in the in- 

 tertubular tissue of the mesonephros. The mononuclears in the 

 kidney were more deeply stained than those found in the liver 

 capillaries. 



