THE PRONEPHROS 



IQ7 



Pronephric duct B 



Mesodermal 

 segments 



Neural tube. 



Anlages of pronephric 

 duct 



Nephrotome 

 Somatic mesoderm 



Splanchnic mesoderm 



Pronephric tubule Ccelom Notochord Entoderm 



FIG. 204. Diagrams showing the development of the pronephric duct and pronephric tubules 

 (modified from Felix). A represents a later stage than B. 



Neural t 



Notochord 



Cavity of gu 



Splanchnic mesodern, 



Mesoderm of yolk sac 



'Mesodermal segment 

 'avity of segment 



Intermediate cell mass 

 Anlage of extremity 



'Ccelom 



JT Somatic mesoderm 

 ) 



Umbilical vein 



FIG. 205. Transverse section of a 2.4 mm. human embryo, showing the intermediate cell mass 

 or nephrotome (Kollmann). 



