320 THE CHICK. 



undergo degenerative changes, and ultimately they become 

 almost completely obliterated on both sides of the body. 



The Wolffian body aborts in great part : a portion of it. 

 however, persists as the epididymis ; while outgrowths from 

 the Malpighian bodies of this portion penetrate into the testis, 

 and become the vasa efferentia. The Wolffian duct persists 

 as the vas deferens, becoming bent on itself into short trans- 

 verse folds along almost its entire length, in the manner so fre- 

 quently seen in the male genital duct both of Vertebrates and of 

 Invertebrates. 



b. In the female, or hen bird, the Wolffian body atrophies, a 

 small part alone persisting as the parovarium. a body lying in 

 the mesentery between the ovary and the kidney, and in which 

 the tubular structure of the Wolffian body remains recognisable 

 even in the adult bird. The Wolffian duct disappears. 



The Miillerian duct of the right side, like the right ovary, 

 disappears, though traces of it may persist in the adult. The 

 left Miillerian duct becomes the oviduct : its peritoneal opening 

 becomes the fimbriated mouth of the oviduct, and its walls 

 thicken greatly, especially at the cloacal end. 



7. The Supra-renal Bodies. 



The development of the supra-renal or adrenal bodies is not 

 very satisfactorily determined. Each consists of two parts, 

 cortical and medullary. Of these, it is generally agreed that the 

 medullary portion arises as a part of the sympathetic nervous 

 system. The cortical portion is developed from groups of cells 

 which appear, about the end of the fourth day, in the mesoblast 

 along the inner side of the Wolffian body, between this and the 

 aorta ; and which increase during the fifth and sixth days so as 

 to form cell masses of considerable size. On the seventh day 

 these masses become closely attached to the Malpighian capsules 

 of the Wolffian body, but whether this is to be interpreted as 

 indicating any essential connection between the two bodies is 

 very doubtful. 



