54 



H. VON W. SCHULTE 



The mantles are clearly demarcated from the lateral meso- 

 cardia by deep sulci so that the junction between omphalo- 

 mesenteric vein and heart tube is deeply indented on each side. 

 From this point the mantles gradually expand again to l^e in- 



Fig. 4 Myoeijit-ardial mantle of a cat embryo of twelve pairs of somites. 

 Cokimbia Collection, No. 547. X 300. Reduced one-half. 1, Middle cardiac 

 plate; 2, y)ull)ns; .?, ventricle; 4. iMilbo-ventricular sulcus; 5, atrio-venous angle; 

 6, shoulder of mantle. 



dented by the deep oblique bulbo-ventricular clefts. Beyond 

 them the truncus has the form of a cylinder, slightly flattened 

 dorso-ventrally, emerging between the high shoulders of the 

 mantles (fig. 4), In this stage the heart is approximately sym- 

 metrical and the bulbo-ventricular sulci of the two sides are in 



