1 62 THE URINOGENITAL ORGANS OF VERTEBRATES. 



FIG. 8. TRANSVERSE SECTION THROUGH THE DORSAL REGION OF AN EMBRYO 

 FOWL OF 45 h. To SHEW THE MODE OF FORMATION OF THE WOLFFIAN 

 DUCT. 



A. epiblast ; B. mesoblast ; C. hypoblast ; M.c. medullary canal; Pv. Pro- 

 tovertebrae ; W.d. Wolffian duct ; So. Somatopleure ; Sp. Splanchnopleure ; //. 

 pleuroperitoneal cavity ; ch. notochord ; ay. dorsal aorta ; T. blood-vessels. 



