BEHAVIOR OF ANURA TOWARD COLLOIDAL DYES 61 



ments seem to show that tissues which ordinarily react in Summer, 

 may not readily react, or may not react at all toward the dye 

 during the Winter months. . 



8. The method of vital staining by colloidal acid dyes presents 

 no evidence whatever in favor of the view, as claimed by Wislocki, 

 that the lymphatics of the frog are derived from the endothelium 

 of the veins. Lymphatic endothelium does not react toward 

 these dyes in the frog and toad until practically all of the main 

 lymphatic channels have been formed and have begun to function 

 in returning lymph from the tissue spaces to the veins. Such an 

 advanced stage of development would not be ordinarily regarded 

 as a favorable one from which to infer in what manner the lym- 

 phatics may have been formed. 



9. Mononuclear leucocytes with eccentrically situated nuclei, 

 appear to be the chief free macrophages found in the tissues of 

 anura which most readily react toward colloidal acid dyes. 



