192 THE THIRD DAY. [CHAP. 



Fia. 66. 



SECTION THROUGH THE EXTERNAL GLOMERULUS OF ONE OF 

 THE ANTERIOR SEGMENTAL TUBES OF AN EMBRYO CHICK 

 OF ABOUT 100 HOURS. 

 gl. glomerulus ; ge. peritoneal epithelium ; Wd. Wolffian duct ; 



ao. aorta ; me. mesentery. 



The Wolffian tubule, and the connection between the external 

 and internal parts of the glomerulus are not shewn in this figure. 



In the case of the remaining tubules developed from 

 the S-shaped cords, the attachment to the peritoneal 

 epithelium is very soon lost. The cords acquire a 

 lumen, and open into the Wolffian duct. Their blind 

 extremities constitute the commencements of Malpi- 

 ghian bodies. 



In the posterior part of the Wolffian body of the 

 chick the intermediate cell-mass becomes very early 

 detached from the peritoneal epithelium, and at a con- 

 siderably later period breaks up into oval vesicles, which 

 elongate into Wolffian tubules. In addition to the 

 primary tubules, whose development has just been 

 described, secondary and tertiary tubules are formed 

 on the dorsal side of the primary tubules. They are 



