The development of the heart of Rana temporaria L.

Summary

	1. The development of the heart of Rana temporaria has been reinvestigated.
	2. While the myocardium, pericardial cavity and pericardium develop from paired lateral anlagen, no evidence for a double origin of the endothelial lining of the heart was found.
	3. The accounts of the formation of the interauricular septum given by Marshall (1893) and Goodrich (1930) are reconciled by a new explanation which takes into account a possible forward rolling movement of the auricles associated with the twisting which takes place in the larval heart during its development.
	4. A new description of the twisting of the heart tube is given which recognises the fact that the conus emerges from the dorsal right-hand corner of the ventricle and not from the ventral right-hand side as shown in older texts.