. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 428 formed the No to chord and the Gastral M esoblast. (See my paper "Further Studies on the Germinal Layers of Chelonia", Journ. Sc. Coll. Tokyo, Japan, Vol. V, Pt. 1.) 5) The floor of the archenteron is divided into two parts: (a) the larger posterior part which proliferates the peristomal mesoblast, and (b) the smaller anterior part, which losing its definiteuess is finally absorbed, together with that part of the primitive knob lying underneath it, thus putting the archenteron in communication with the large sub
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 428 formed the No to chord and the Gastral M esoblast. (See my paper "Further Studies on the Germinal Layers of Chelonia", Journ. Sc. Coll. Tokyo, Japan, Vol. V, Pt. 1.) 5) The floor of the archenteron is divided into two parts: (a) the larger posterior part which proliferates the peristomal mesoblast, and (b) the smaller anterior part, which losing its definiteuess is finally absorbed, together with that part of the primitive knob lying underneath it, thus putting the archenteron in communication with the large subgerminal ca- vity in the yolk (fig. 4). 6) The primitive knob which was gradually spreading itself beneath the embryonic shield before the breaking through of the archenteric cavity continues to do so after that event, until the whole of the ventral surface of the embryonic shield has been covered when the process stops (fig. 5). The advance of the cells of the primitive knob is in its later stages marked by a peri pheral reticulated zone with a compact central area. (See figs. 4 b—13 b of Mehnert's "Gastru- lation u. Keimblätterbildung der Emys lutaria taurica". Morph. Arbeiten, herausgeg. v. Dr. G. Schwalbe , I. Bd., 3. Heft. Mehnert gives a difterent inter- pretation to this appearance.) 7) At some distance back from the anterior end of the embryonic shield, the head-fold is seen developed (fig. 6 Hd. fd.). As the primitive knob marks the posterior end of the embryo and the lateral folds arise within the embryonic shield, the conclusion is reached that the future embryo-body is developed entriely within the area covered ven- trally by the part derived from the primitive knob. If we put the results in another way, they may be summed up as follows: From the epiblast of the embryonic shield,. EmhT. shi'clei ~ "B A^che. - Arc/renf&ron,, Lryon'C SftietcC. Please note that these images are extracted from scanned page images that may have been digitally enhanc
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