. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 84 J- THOS. PATTERSON. cubated blastoderm just inside the lateral margins of the area pellucida (Fig. i, A). Such injuries effect a fusion between the ectoderm and entoderm,1 and thus put up a barrier beyond which. A B C D FIG. i. A-B are schemes for operating in Experiments respectively. the primitive streak mesoblast cannot pass in its peripheral extension. The embryo, as it appears after forty-eight hours of incuba- tion, is shown in Fig. 2. Instead of being circular in outline, as under normal conditions, the vasc
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 84 J- THOS. PATTERSON. cubated blastoderm just inside the lateral margins of the area pellucida (Fig. i, A). Such injuries effect a fusion between the ectoderm and entoderm,1 and thus put up a barrier beyond which. A B C D FIG. i. A-B are schemes for operating in Experiments respectively. the primitive streak mesoblast cannot pass in its peripheral extension. The embryo, as it appears after forty-eight hours of incuba- tion, is shown in Fig. 2. Instead of being circular in outline, as under normal conditions, the vascular area is in the form of a figure eight, the vena terminalis baying in on each side around the obstructing injury-scars. It is easy to see how this result was brought about. The lateral edges of the mesoblast, grow- ing out from the primitive streak, came in contact with the two injuries and at these points the mesoblast was prevented from spreading farther, and so from coming in contact with the germ-wall. There has been also a decided retardation in the spreading of the mesoblast adjacent the injuries. Hence, the transverse diameter of the vascular area, even at the widest points, is only 8 mm., while the longitudinal diameter is 13 mm. The interesting point brought out by this experiment is made evident when one turns to a study of a section taken across one of the bays (Fig. 3, line A-B). The portion of the germ-wall, which lies between the two sections of the vena terminalis, re- mains undifferentiated (Fig. 4), that is, it has not given rise to vascular mesoblast. It should be noted that it is from this region of the germ-wall that the primitive streak mesoblast has 1 The methods employed in this work have already been described in the following papers : Patterson, J. T., " The Order of Appearance of the Anterior Somites in the Chick," BIOL. BULL., Vol. 13; " Gastrulation in the Pigeon's Egg—A Morphological and Experimental Study" (in press), Jour
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
