DEVELOPMENT OF GALLUS 



221 



branching to a number of Bowman's capsules, and each be- 

 coming vascularised by a glomerulus becomes a Malpighian 

 corpuscle. The mesonephros is the functional kidney of the 

 embryo, and is therefore present in the early life of both sexes. 

 Later, it is preserved only in the male, for it establishes con- 

 nexion with the testis by means of the vasa efferentia, and the 

 Wolffian duct functions as the vas deferens. It disappears 

 in the female. 



The kidney of the adult is the metanephros. It is formed 

 after the mesonephros, and at a time when the segmental 



Fig. 105. — Longitudinal section through a metanephric kidney. 



Showing the Malpighian corpuscles (Mc) in communication with the 

 ureter (w) by means of the collecting tubules (ct) ; ra, renal artery. 



arrangement of the intermediate cell-mass has been lost. A 

 diverticulum develops from the base of the Wolffian duct, 

 near the cloaca ; this is the ureter. The ureter grows forwards 

 dorsal to the mesonephros, and branches repeatedly forming 

 a large number of collecting tubules. The metanephric 

 tubules, or Bowman's capsules, arise from an indistinct heap of 

 cells of the intermediate cell-masses belonging to one or two 

 segments of the hinder region of the body, and called simply 

 the metanephrogenous tissue. These capsules hollow out and 

 connect with the collecting tubules which were formed by the 



