DEVELOPMENT OF KIDNEYS AND FAT-BODIES IN THE FFvOG. 153 



Concerning the mode of formation of the nephrostomial tubules, 

 our observations are also incomplete. The tubules appear to us to 

 arise as solid rods of cells in the mesoblast, continuous with the 

 strings of cells which give rise to the Wolffian tubules. These soon 

 acquire connection with the peritoneum, the peritoneal epithelium 

 however taking no part in their formation, and the whole of the 

 epithelium of the tubule being derived from the solid rod of meso- 

 blast cells. The lumen of the tubule is formed as a split between the 

 inner ends of the cells of the rod, and not by invagination of the 

 peritoneum. 



We have not ourselves seen at any stage a tubular communication 

 between the nephrostome and the neck of the Malpighian body, or 

 indeed with any other part of a urinary tubule. Nussbaum's 

 description and figures of the early communication with the neck of 

 the Malpighian body are, however, very precise, and they have 

 been confirmed by Hoffmann.* Bearing in mind also that Spengel 

 and Nussbaum's descriptions show conclusively that in Urodeles this 

 connection between the nephrostomial tubule and the neck of the 

 Malpighian body is not only present in the larva, but persists 

 throughout life, we are inclined to believe that it really occurs in 

 young Anuran tadpoles, though it can only be present for a very 

 short period, and may perhaps not be acquired in all cases. If this 

 view is correct, we have in the relations of the nephrostomial tubules 

 another instance of a curiously specialised condition in Anura, 

 derived from a more primitive condition which is still retained by 

 the Urodeles. 



III. The Development of the Fat-bodies. 



Von Wittichf first described the fat-bodies of Amphibians as 

 formed by fatty degeneration of the anterior ends of the genital 

 ridges. 



Giles I has recently questioned the accuracy of this determination, 



* Hoffmann, loc. cit, pp. 593, 594. Hoffmann maintains that in the adult Anura 

 the nephrostomial tubules end blindly. 



t VonWittich, "Beitrage zur Mbrphologischen und Histologischen Entwiekelung 

 der Harn, und Geschlechtewerkzeuge der nackten Amphibien;" "Zeitschrift f. 

 wiss. Zoologie," Bd, iv., 1853, pp. 148, 149. 



t Giles, "Development of the Fat-bodies in Rana temporaria;" "Quarterly 

 Journal of Microscopical Science," vol. xxix., 1888, pp. 133-142, reprinted in the 

 pre 'nt volume. 



