78 



EDWAED MCCRADY, JR. 



is accomplished without the formation of a ventral meso- 

 cardium at any time. This is illustrated in figure 26. The 

 chick sections, taken from Patten's Early Embryology of the 

 Chick, are presented for comparison. It will be seen that in 



Chick 



(after fatten) 



P 



Ti/slon or 

 a/red Herni'cardia 



in 



Chick and Opossum 



H 



Fig. 26 Sectional views of opossum embryos of stages 24 to 26 and chick 

 embryos (25 to 28 hours) to show that no ventral mesoeardium ever forms in 

 the opossum. 



