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H. VON W. SCHULTE 



tions into tlie shoulders of the mantles. The projection on the 

 left side is long and pointed, that of the right blunt and short 

 conformably to the alteration in shape of the mantles at this 



Fig. 14 Photomicrograph of section through the bulbs of embryo shown in 

 figure 13. X 125. Reduced one-half. 1, right bulb; 2, left bulb; 3, shoulder of 

 left ventricle myocardium. 



period. Coalescence has been effected at about the middle of 

 the ventricles. Immediately ^-entrad of this area is a region 

 where the endothelium of the tubes is not yet in contact and a 

 perforation extends through the heart from the convexity to the 



