Urinary 

 papilla 



^Developing mesonephros 

 ""Pronephros "^Proriephric duct 



Nerve cord 



Dorsal aori 

 Renxilarterir^ / \ 



Cardinal vein 



Xotochord 

 Myotome 



Glomerulus 



Pronephric 

 duct 



Nephrostome 



Fig. 140. Pronephros. Top, tadpole with body wall and viscera removed 

 to show the position of the pronephros and pronephric ducts. The meta- 

 meric mesonephros is shown bcsiinning its development. Bottom, a diagram- 

 matic cross section of a dogfish embryo, showing the structure and position 



of the pronephros. 



