66 H. VON W. SCHULTE 



venous angles are greatly deepened and the omphalo-mesenteric 

 veins are brought close together. Between their approximated 

 portions a small communication has formed. As a whole the 

 right tube is larger, perhaps more distended than the left. The 

 right omphalo-mesenteric vein is certainly larger than that of 

 the opposite side. 



Fig. 12 Photomicrograph of section of heart shown in figure 11. X 125. 

 Reduced one-half. 1, Middle cardiac plate; 2, median angiocyst; 3, ventricle. 



In the heart of the embryo of 14 somites as marked changes 

 have supervened in the endothelial tubes as in the myocardium. 

 The loop is well formed but in its entire length is double, being 

 composed of two parallel tubes as yet only at the beginning of 

 fusion. The general configuration is shown in figure 13, in 

 which the model is seen from behind and slightly from above, 

 bringing its caudal aspect prominently into view and to a less 



