60 CHARLES F. W. McCLURE 



regions of the pharynx. These leucocytes are even found in the 

 epithelial layer itself where it is not unlikely that they actually 

 ingest the dye particles previously stored by the epithelial cells 

 of the pharynx. 



14. SUMMARY 



1 . Among 140 larvae of Buf o which were placed on the third and 

 fourth days after fertilization in solutions of colloidal acid dyes 

 (Niagara and trypan blue), it was found that dye was stored in 

 certain typical tissues of only 3 of the 66 larvae killed at successive 

 intervals previous to the ninth day. In all except 2 of the 31 

 larvae killed on the ninth day, and in all of the 43 larvae killed at 

 successive intervals subsequent to this time, dye was stored in the 

 form of dye granules in the cytoplasm of certain typical cells. 



2. Essentially similar results were obtained with frog larvae. 



3. These experiments indicate that the initiation of the process 

 by which colloidal acid dye particles are stored in the cytoplasm of 

 the cell, must be associated with the attainment of some dis- 

 tinctive ontogenetic larval stage, rather than with the length of 



. time larvae are acted upon by dyes. 



4. The initiation of the process of ingestion of colloidal acid 

 dyes particles by the macrophages and of their absorption by 

 renal epithelium, appears to be coincident with the establishment 

 in the embryo of a continuous lymph flow through the lymphatics, 

 between the tissue spaces and the veins. 



5. After the critical ontogenetic stage has been passed, the 

 storage of colloidal dye particles by typical tissues may be accom- 

 plished within a relatively short time in both larval and adult 

 frogs and toads. 



6. Experiments on larval and adult frogs and toads show that 

 colloidal acid dye solutions can gain entrance to the body through 

 the integument. Feeding experiments on adults also show that 

 colloidal acid dye solutions may be absorbed by the intestinal 

 mucosa and reach the general circulation by the portal vein. 



7. During the Winter the reactions of the tissues in adult frogs 

 and toads toward colloidal acid dyes appear to be much less 

 pronounced than in the Spring and Summer. Immersion experi- 



