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; CceL, 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 



