ing gs, the bilobed arch sh, The primitive shell-sac or enteron or lateral vesicles shell-gland ° of invaginated endoderm, pi, The rectal peduncle or whichwill develop into liver.
Not only is the coelom thus subdivided, but the enteron (gut, alimentary canal, digestive tube) itself shows indications of three main subsections in continuity with one another: - (I) proboscis-gut (Eicheldarm, stomochord, vide infra); (2) collar-gut (buccal cavity, throat); (3) truncal gut extending from the collar to the vent.
The enteron itself becomes bilobed and is joined by a new invagination, that of the mouth and stomodaeum.
The careful study of the development of one Acoelous form and of certain Rhabdocoels has strengthened this hypothesis by showing that no definite enteron or gut is at first laid down, but that certain embryonic syncytial tracts become digestive tracts, others excretory, others again muscular.
EA x,Axial enteron.
ing gs, the bilobed arch sh, The primitive shell-sac or enteron or lateral vesicles shell-gland Ã‚° of invaginated endoderm, pi, The rectal peduncle or whichwill develop into liver.
The enteron arises as a space in the endoderm, and an opacity - the primitive streak - appears at the hind end of the blastopore (fig.
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