. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 351 adduced by these authors and pointed out the objections to considering them as illustrative of normal developmont. Morgan i) has more recently pointed out others. The observations of von Baer, Reichert, Newport, PflIIger and others foreshadowed the inadequacy of the theory when applied to the Amphibia, while the evidence adduced by 0. Schultze, Assheton, H. V. Wilson and myself have shown that it is no longer tenable. In the accompanying diagrams (Figs. 28—31) I have endeav- ored to point out some of the more important ch
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 351 adduced by these authors and pointed out the objections to considering them as illustrative of normal developmont. Morgan i) has more recently pointed out others. The observations of von Baer, Reichert, Newport, PflIIger and others foreshadowed the inadequacy of the theory when applied to the Amphibia, while the evidence adduced by 0. Schultze, Assheton, H. V. Wilson and myself have shown that it is no longer tenable. In the accompanying diagrams (Figs. 28—31) I have endeav- ored to point out some of the more important changes which have been brought about in the formation of the ^8 ^^ embryo through a con- stantly increasing amount of yolk ma- terial as compared with the amount of germinal material. In general the views are those expressed in a previous paper. The experiments on Nec- turus, however, lead me to qualify some whatmy previous sta- tements regarding the formation of the Am- phibian embryo. Fig. 28 represents the conditions observed in Rana, Bufo, Acris and Chorophilus. The blastodisc, represented by the dotted area, has extended well over the yolk, reaching the line B. I. before the body of the embryo is differentiated. When the embryo is first discernable it extends from Ä to B. as conclusively shown from previous experiments. This portion, represented by the broad black line, is differentiated in situ. A small portion of the embryo is formed through a backward extension of the dorsal lip of the blastopore. This I have represented by cross lines. I would not maintain that the relative extent is precisely shown in the diagram, but would thus emphasize the fact that a part of the embryo is formed in this manner. The remainder of the embryo (P. S.) is formed by the concrescence of the marginal thickening of 1) The Formation of the Fish Embryo. Journ. Morphol. Boston, Vol. 10, 1895, p. . Please note that these images are extracted from scanned page images that may have b
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