. The elements of Embryology,. v.] THE TAIL-FOLD. 125 the whole archiblastic framework of the embryo became riddled by a network of parablast. From these parablastic elements he considered there arose not only the epitheKum (endothelium) of the blood-vessels and lymphatic spaces, but also all the connective-tissue elements of the body, the archiblast being represented in the vessels of the adult body by the muscular fibres alone. 17. As we stated above (p. 87), the folding in of the splanchnopleure to form the alimentary canal is proceeding with great rapidity, the tail-fold as well as the hea
. The elements of Embryology,. v.] THE TAIL-FOLD. 125 the whole archiblastic framework of the embryo became riddled by a network of parablast. From these parablastic elements he considered there arose not only the epitheKum (endothelium) of the blood-vessels and lymphatic spaces, but also all the connective-tissue elements of the body, the archiblast being represented in the vessels of the adult body by the muscular fibres alone. 17. As we stated above (p. 87), the folding in of the splanchnopleure to form the alimentary canal is proceeding with great rapidity, the tail-fold as well as the head-fold con- tributing largely to the result. The formation of the tail-fold is very similar to that of the head-fold. At the extreme hind end of the embryo, at the tip of the tail (Fig. 40, f), there is no cleavage of the mesoblast, and therefore neither somatopleure nor splanchno- pleure. The tail is a solid, somewhat curved, blunt cone of mesoblast, immediately coated with the superficial epiblast Fig. Section of the Tail-end of an Embeto (Chiok) of the Thied Day. (From Dobrynin.) t. the tail. So. somatopleure. Spl. splanchnopleure. pp. pleuroperitoneal space. The letters G and Dd are placed within the alimentary canal: a more detailed explanation of the figiu-e is given under Fig. 50. except at the upper surface (corresponding to the back of the embryo), where lies the pointed termination of the neural tube. At some little distance forwards, towards the head, the cleavage of the mesoblast begins, and the somatoplevire diverges from the splanchnopleure, the latter, as in the head- fold, being folded in to a greater extent than the former. Ex- cept for the absence of the cephalic enlargement of the neural tube, the presence of distinct protovertebrce up to nearly the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the or
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