140 PROFESSOR MARSHALL AND EDWARD J. BLES. 



in other parts the tubules are of very irregular size, and often laterally 

 compressed. The walls of the tubules, and more particularly of 

 those which are most dilated, have also undergone important changes. 

 While in the earlier stages each tubule is lined by a single layer of 

 cubical cells, with clearly defined outlines, at the present stage the 

 epithelial cells are cloudy in appearance, with ill-defined and often 

 indistinguishable boundaries, while their inner surfaces, facing 

 towards the cavity of the tubule, have exceedingly ragged and 

 irregular outlines. Within the tubules are found at intervals larger 

 or smaller masses of debris, apparently resulting from the breaking 

 down of some of the epithelial cells. The three nephrostomes are still 

 present (Fig. 6, N T), and communicate with the tubules by narrow 

 nephrostomial tubes lined by pigmented epithelial cells bearing 

 flagella, as in the earlier stages. 



The dilatation of the tubules is most marked, not in the main 

 tubes, but in the lateral diverticula, which, we have seen, end 

 blindly. It is worthy of notice, that although the epithelium of the 

 tubules is clearly degenerating, yet that there is no sign whatever of 

 fatty degeneration, such as has been described by Duval* and other 

 writers. The appearances rather suggest that the changes are caused 

 by accumulation of fluid within the tubules, and especially their blind 

 diverticula, due perhaps to obstruction, partial or complete, of the 

 duct ; the result of this accumulation of fluid being first dilatation of 

 the tubules, and then disintegration of their living epithelium. 



A comparison of our specimens and figures with the figures given 

 by Selenkaf of the head kidney in the tadpole of Hylodes Martini- 

 censis at a slightly earlier stage of development, strongly suggests 

 that in this latter case also the tubules are in the state of dilatation 

 immediately preceding degeneration and atrophy. Selenka figures 

 the tubules as of very unequal size, the lateral diverticula being 

 especially large. 



From this stage the head kidneys of the tadpole steadily 

 degenerate. In tadpoles of 40 mm. length they are still spherical 

 bodies of fair size (Fig. 1, N A), though much smaller both 

 relatively and absolutely than before. All three nephrostomes are 

 present, and open freely into the tubules. The tubules are irregular 



* Duval, loc. cit., p. 28. 



t Selenka, loc. cit., Figs. 1, 2. 



