T H E first of this series of papers (Bellairs, 1953) outlined the morphological changes occurring in the endoderm of the chick up to the stage of about ten pairs of somites; it also showed that the presumptive foregut area in the primitive streak stage blastoderm lies around the anterior end of the primitive streak, and at a slightly later stage around the head process. The present paper is co...

The hepatic, splenic and left gastric arteries are considered as the ‘‘main classic branches’’ of the celiac trunk (CT). In the embryonic life, yolk sac is supplied by vitelline arteries. Later they gradually fuse and help in formation of the arteries dorsal to the mesentery of the gut. In the adult, they are developed as CT, superior mesenteric and inferior mesenteric arteries. These vessels s...