154 PROFESSOR MARSHALL AND EDWARD J. BLES. 



holding that the fat-bodies are really formed by fatty degeneration of 

 the head kidneys, and that their connection with the genital organs 

 is a secondarily acquired one. 



We have investigated the point, and find that von Wittich's 

 account is correct. 



Fig. 1 represents, as already noticed, a 40 mm. tadpole dissected 

 from the ventral surface. The condition of the urinary organs has 

 been sufficiently described above. The genital organs, G R, are 

 present as a pair of narrow ridges lying along the sides of the aorta 

 and the inner borders of the Wolffian bodies. The anterior part 

 of each ridge, G F, is separated by a slight constriction from the 

 posterior part, and is notched at its free edge into a few small, 

 irregular lobes. This anterior part of the genital ridge is the com- 

 mencing fat-body ; it is, as von Wittich correctly described, almost 

 invariably larger on the left side than the right. 



Figs. 8 and 9 represent transverse sections passing respectively 

 through the fat-bodies and through the genital organs of a tadpole 

 of the same age as Fig. 1 ; the levels at which the sections are taken 

 being indicated by the lines a a, bb, in Fig. 1. 



The fat-bodies (Fig. 8, G F), which along the greater part of their 

 length lie alongside the archinephric ducts, but in front of the 

 Wolffian bodies, are seen to have a very similar appearance, and pre- 

 cisely the same relations, as the genital organs in Fig. 9, G R ; while 

 Fig. 1 shows how far they are really removed from the head 

 kidneys. 



At this period the fat-body consists of a solid mass of closely 

 packed cells, in which the deposition of fat is only just commencing. 



The condition in a tailed frog is shown in Fig. 5, in which the 

 head kidneys, N A, have almost completely disappeared ; while the 

 fat-bodies, G F, have increased greatly in size, and are produced at 

 their free ventral borders into finger-like lobes. The fat-body of the 

 left side is still markedly larger than that of the right side. 



Giles' error appears to have arisen from his removing the kidneys 

 and genital organs before cutting them into sections, and so over- 

 looking the real position and relations of the head kidneys in the 

 tailed frog, and mistaking for them the degenerating tubules of the 

 anterior end of the Wolffian body, in which true fatty degeneration 

 occurs as he correctly describes ; while Figs. 8 and 9 show how 



