THE LATER DEVELOPMENT OF THE CHICK 357 



(Fig. 140). This rudiment then extends upward to the Wolffian 

 duct with which it communicates. On the side opposite this 

 extension another outgrowth appears which forms the Mal- 

 pighian body. 



FIG. 140. The development of the mesonephros. A, B. Transverse sections 

 through the mesonephric tubules of the duck embryo with forty-five pairs of 

 somites. After Schreiner. C. Transverse section through the middle of the 

 mesonephros of a chick of ninety-six hours. From Lillie (Development of the 

 Chick). Ao., Dorsal aorta; B., rudiment of Bowman's capsule; c., collecting 

 duct; Cad., ccelom; Col. T., collecting tubule; d., dorsal outgrowth of the Wolffian 

 duct; Glom., glomerulus; germ. Ep., germinal epithelium; M's't., mesentery; 

 n.t., nephrogenous tissue; r., rudiment of conducting portion of primary tubule; 

 T.I, 2, 3, primary, secondary, and tertiary mesonephric tubules; V.c.p., posterior 

 cardinal vein; W.D., Wolffian duct. 



From the nephrotome, just above the primary tubule, 

 several additional secondary mesonephric tubules are formed, 

 and finally, other dorsal tertiary tubules are added, so that six 



