. Journal of morphology . >ceding. Note especially the cells organizing about the periblastic nucleiat ce, and also the two degenerating periblastic nuclei dm), x 365. Fig. 5. Posterior end of a section, five sections to the right of the pre-ceding. This shows the tip of the right horn of the zone of junction, x 365(see also Fig. VI). Fig. 6. A group of six (three shown in the section) cells organized . ^tperiblastic nuclei, which are in the central periblast, x 657. Fig. 7. A normal periblastic nucleus which was introduced for compari-son with the following figures (8-13). X 886. Figs. 8-1
. Journal of morphology . >ceding. Note especially the cells organizing about the periblastic nucleiat ce, and also the two degenerating periblastic nuclei dm), x 365. Fig. 5. Posterior end of a section, five sections to the right of the pre-ceding. This shows the tip of the right horn of the zone of junction, x 365(see also Fig. VI). Fig. 6. A group of six (three shown in the section) cells organized . ^tperiblastic nuclei, which are in the central periblast, x 657. Fig. 7. A normal periblastic nucleus which was introduced for compari-son with the following figures (8-13). X 886. Figs. 8-13. Various stages of degenerating periblastic nuclei, x 886. Fig. 14. Posterior end of a longitudinal section taken slightly to theleft of the median line. It shows the thin epithelial-like margin just beforeinvagination occurs. At iii is one of the few yolk masses that are foundat this stage, x 259. (See also Figs. 30 and VII). Gastrulatioii in the Pi//roiis Egg.,./ T. Patterson. PI. I „„ nn z pn & • • pn pn. Joiirnul of Morphfihgy. Vol. XX Wtmrr i WMtr FrMifjn *M Plate II. Fig. 15. Posterior end of an oblique section from a blastoderm takenthirty-four hours after fertilization, or seven hours before laying. Theyolk is cracked and as a result granules are found in the cavity (c) justposterior to the dorsal-lip. Sec text for description, and also Fig. 339. Fig. IC—Posterior end of a section taken through y-y. Fig. VITT. The sec-tion ends with a thin free marghi. x 259. Fig. 17. Posterior end of a section slightly to the right of the one repre-sented in Fig. 14. It shows how a considerable cavity may develop beneaththe margin before invagination begins, x 259. Fig. 18. Anterior third of a section taken in the plane passing throughCR of Fig. XI. The thinning-out is in the last stages, and at the pointsmarked s a few cells have loosened and sunk down. Otherwise the sub-germinal cavity contains no nucleated cells—only large yolk masses arepresent, some of which a
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