224 THE FOURTH DAY. [CHAP. 



of the changes, which on the attainment of the adult 

 condition take place in the parts described. 



The Wolffian body, according to Waldeyer, may be 

 said to consist of a sexual and urinary part, which can, 

 he states, be easily distinguished in the just-hatched 

 chick. The sexual part becomes in the cock the after- 

 testes or coni vasculosi, and consists of tubules which 

 lose themselves in the seminiferous tubules. In the 

 hen it forms part of the epoophoron 1 of Waldeyer, and 

 is composed of well-developed tubes without pigment. 

 The urinary part forms in both sexes a small rudiment, 

 consisting of blindly ending tubes with yellow pigment ; 

 it is most conspicuous in the hen. This rudiment 

 has been called by Waldeyer parepididymis in the male 

 and paroophoron in the female. 



The Wolffian duct remains as the vas deferens in 

 the male. In the female it becomes atrophied and 

 nearly disappears. 



The duct of Miiller on the right side (that on the 

 left side with the corresponding ovary generally dis- 

 appearing) remains in the female as the oviduct. In 

 the male it is almost entirely obliterated on both 

 sides. 



Vascular system. We may return to the changes 

 which are taking place in the circulation. 



On the fourth day, the point at which the dorsal 

 aorta divides into two branches is carried much further 

 back towards the tail. 



A short way beyond the point of bifurcation, each 

 vessel gives off a branch to the newly-formed allantois. 



1 This is also called parovarium (His), and Bosenmiiller's organ. 



