126 ARTHUR E. GILES. 



invades them, but their protoplasm becomes replaced by it. At a 

 later stage the contents of the cell consist only of fatty granules and 

 granular detritus. 



For a while the outlines of the convoluted tubules can still be 

 made out as in Fig. 6, the line of distinction between normal and 

 degenerated kidney being well marked. But soon all trace of 

 structure disappears, and there remains only a uniformly granu- 

 lar looking mass, as in Fig. 2. This is the fat-body, or corpus 

 advposum. 



We have thus answered the first question that we proposed, "How 

 come the fat-bodies to be in relation with the anterior end of the 

 kidneys 1 " There further remains to be considered the question, 

 " How does the transition from this condition to that found in the 

 adult take place ? " 



When the hind limbs of the tadpole have appeared they develope 

 fairly rapidly, the fore limbs sprouting out somewhat later. The 

 condition of the " tailed frog " is now attained. While this is going 

 on a change takes place in the urino-genital organs, which, as regards 

 the time at which it occurs, varies somewhat in different tadpoles, 

 but usually begins during the period in which the tail is commencing 

 to atrophy, and is for the most part completed by the time the tail 

 is quite absorbed. 



This change is as follows : The anterior end of the nephros grows 

 ventrally, and becomes secondarily attached to the anterior end of 

 the genital organ, ovary or testis, as the case may be. Fig. 7 shows 

 the urino-genital organs during this intermediate stage of transition, 

 the fat-body (/) being directly continuous both with the kidney (k) 

 and with the genital organ (g). 



This occurs at about the time that the mesonephric tubules are 

 growing out towards the genital organ, forming the future vasa 

 efferentia in the case of the male. Thus, in some sections the 

 condition of this double outgrowth from the excretory to the genital 

 organs can be seen, the three parts of the nephros, pro-, meso-, and 

 meta-, being quite continuous. 



Ultimately the attachment of the fat-body to the kidney gives 

 way, and the former remains attached to the anterior end of the 

 genital organ, as it is in the adult (Figs. 8 and 9). We thus see 

 that the fat-body is not the anterior end of the genital organ, which 



