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EDWARD MCCEADY, JR. 



empties into the sinus venosus. This condition persists in 

 the adult, for the two precavae do not develop any cross an- 

 astomosis as in Eutheria but remain permanently inde- 

 pendent of each other. The left precava thus serves to drain 



Fig. 59 Photograph by Dr. A. A. Zimmermann of a section through the cloaca 

 in specimen 16175 showing entry of ureters into clocal horns medial to wolffian 

 ducts. No miillerian ducts are present. 



the blood from the left wall of the heart, but at the same time 

 retains its original function of draining the left side of the 

 head and neck. It is thus both coronary sinus and precava. 



