100 



Georee Heuer*. 



Fig. 4. — Embrj^o pig 4.5 cm. long to show an injection of the retroperitoneal 

 sac and mesentery made through the thoracic duct, x 2.5. K., kidney ; r. o., 

 reproductive organ ; r. s., retroperitoneal sac ; sp., spleen ; s., stomach ; W. b.. 

 Wolffian body. 



