262 EDEMA IN LARVAL AND ADULT ANURA 



tubules which normally constitute the greater portion of the kidney 

 and which occupy a medial and ventral position. In some larvae none 

 of these particular tubules had even been developed. In all other 

 cases, in which only their partial development had occurred, the few 

 tubules present were always greatly hypertrophied and were often 

 lined by an exceedingly thin-layered epithelium which closely re- 

 sembled endothelium in appearance. 



The less extensive tubular complex which normally occupies a 

 dorsolateral position in the pronephros and into which the nephros- 

 tomal canals directly open was, however, invariably found to be de- 

 veloped to a considerable degree in all the edematous larvae exam- 

 ined. It was lined by a thick-layered epithelium which is the only 

 epithelium of the pronephros in the writer's experience, in both nor- 

 mal and edematous frog or toad larvae, that has thus far been ob- 

 served to absorb colloidal acid dyes. In all cases this dorsolateral 

 tubular complex was found to be much hypertrophied and often blad- 

 der-like in appearance and, together with the three nephrostomal 

 canals which open into it, was occasionally found to constitute the 

 only portion of the kidney that had been formed. In such extreme 

 cases the pronephric duct was either a solid structure or was not 

 connected with the kidney at all. 



Associated with this general defect in kidney development the 

 lymph sinuses of the body, especially those of the head region, were 

 often found to be greatly distended with fluid. In larvee of Type 1 

 in which the edema is generalized, no defect in the development of 

 any organs of the body was evident except that of the pronephric 

 tubules referred to. In some cases (Type 2) the anterior lymph 

 hearts were absent, and other prominent defects in the vascular sys- 

 tem met with which need not be mentioned here. The pericardial 

 and coelomic cavities were often greatly expanded and blebs or blis- 

 ters of various sizes were occasionally formed under the epidermis. 

 All these cavities were filled with fluid, as could easily be determined 

 in larvas which had been placed in solutions of colloidal acid dyes. 



We know that water and certain colloidal acid dyes^ are continu- 



^ McClure, C. F. W., On the behavior of Bujo and Rana toward colloidal 

 dyes of the acid azo group, Memoirs of The Wistar Institute of Anatomy and 

 Biology, No. 8, Philadelphia, 1918. 



