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H. VON W. SCHULTE 



collection of fluid and are modified to endothelium. I should 

 prefer, therefore, to term MoUier's first stage of solid cords, so 

 far as the mammal is concerned, simply mesenchyme. His sec- 

 ond 'mesenchymatous' stage is really a mixed condition of mes- 

 enchyme and endothelial vesicles; it might be termed the stage 



Fig. 9 Reconstruction of endothelial heart tubes and adjacent mesenchyme 

 of a cat embryo of eleven pairs of somites. Columbia Collection, No. 534. X 

 300. Reduced one-h;iIf. 7, Bulb; 2, isthmus, corresponding to bulbo-ventric- 

 ular sulcus; 3, ventricle: 4. umphalo-mesenteric vein; 5, atrio-venous angle; 6, 

 mesenchyme between tul)es; 7, anterior intestinal portal; 8, oral plate. 



