Grey Crescent Research Articles

The Determination of the Neural Plate in Urodeles

Previous articleNext article No AccessThe Determination of the Neural Plate in UrodelesFrancis G. GilchristFrancis G. Gilchrist Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 4, Number 4Dec., 1929 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/394346 Citations: 7Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Mabel C. Paterson Animal-vegetal balance in amphibian development, Journal of Experimental Zoology 134, no.11 (Feb 1957): 183–205.https://doi.org/10.1002/jez.1401340110K. R. PORTER DIPLOID AND ANDROGENETIC HAPLOID HYBRIDIZATION BETWEEN TWO FORMS OF RANA PIPIENS, SCHREBER, The Biological Bulletin 80, no.22 (Sep 2016): 238–264.https://doi.org/10.2307/1537601A. Mandel Schbchtman Relation between the grey crescent and the organizer center of a urodele egg (Triturus torosus), Wilhelm Roux' Archiv f�r Entwicklungsmechanik der Organismen 134, no.11 (Jan 1936): 207–208.https://doi.org/10.1007/BF00573471Francis G. Gilchrist The time relations of determinations in early amphibian development, Journal of Experimental Zoology 66, no.11 (Aug 1933): 15–51.https://doi.org/10.1002/jez.1400660103 Kathryn F. Stein The Location and Differentiation of the Presumptive Ectoderm of the Forebrain and Hypophysis as Shown by Chorio-Allantoic Grafts, Physiological Zoology 6, no.22 (Sep 2015): 205–235.https://doi.org/10.1086/physzool.6.2.30151197Walter Altekr�ger �ber den Einfluss experimentell erzeugter Form�nderungen auf die Induktionsf�higkeit von Organisatoren, Wilhelm Roux' Archiv f�r Entwicklungsmechanik der Organismen 126, no.11 (Jan 1932): 1–18.https://doi.org/10.1007/BF00586373Gerhard Fankhauser Die Entwicklungspotenzen diploidkerniger H�lften des ungefurchten Tritoneies, Wilhelm Roux' Archiv f�r Entwicklungsmechanik der Organismen 122, no.44 (Jan 1930): 671–735.https://doi.org/10.1007/BF00575208

The relation between normal and abnormal development of the embryo of the frog

The results show that by removing the material of the top of the egg much of the embryo-forming-substance is lost, and although these eggs were kept for some time the dorsal parts of the embryo did not appear. The region of the blastoporic lip is usually left, and invagination takes place. The process of invagination is apparently independent of the presence of embryo-forming material anterior to the region of gastrulation. The results indicate, if they do not prove, that the material of the gray crescent is less often lost than the material of other parts of the egg, and it is not improbable that this may be due to its being more tenacious, so that it does not exude when the other substances flow out of the opening. A ring of similar substance must be supposed to exist around the egg, so that the blastoporic rim also often develops; but the material on the posterior side is more often lost than that of the ring elsewhere. While the results support, in general, the conclusions reached in the VI paper of this series, yet taken alone they are too fragmentary to establish the above mentioned conclusions, and the operation itself is too uncertain to draw further inferences than those indicated above. Nevertheless it is certainly significant to find that when the material of the top of the egg is lost, the dorsal structures fail to put in an appearance, while the gastrulation process begins independently of their presence or absence.

The relation between normal and abnormal development of the embryo of the frog

The results show that by removing the material of the top of the egg much of the embryo-forming-substance is lost, and although these eggs were kept for some time the dorsal parts of the embryo did not appear. The region of the blastoporic lip is usually left, and invagination takes place. The process of invagination is apparently independent of the presence of embryo-forming material anterior to the region of gastrulation. The results indicate, if they do not prove, that the material of the gray crescent is less often lost than the material of other parts of the egg, and it is not improbable that this may be due to its being more tenacious, so that it does not exude when the other substances flow out of the opening. A ring of similar substance must be supposed to exist around the egg, so that the blastoporic rim also often develops; but the material on the posterior side is more often lost than that of the ring elsewhere.

The relation of the first plane of cleavage and the grey crescent to the median plane of the embryo of the frog

1) When the first plane of cleavage coincides with the median plane of the grey crescent, the median plane of the embryo coincides with these two. li]2)|When the first plane of cleavage is at right angles to the median plane of the grey crescent, the median plane of the embryo usually coincides either with the first plane of cleavage or with the median plane of the grey crescent, but sometimes with neither. li]3)|The dorsal lip of the blastopore appears on the grey crescent side of the egg. li]4)|In fifty percent of the cases the first plane of cleavage coincides with the median plane of the grey crescent. In about eight and a half per cent of the cases the second plane of cleavage coincides with the median plane of the grey crescent. In the remaining eggs, the first plane of cleavage lies to one side, or the other, of the middle of the grey crescent, usually near to it. li]5)|The smallest black Gell of the four at the eight cell stage always lies on the crescent side of the egg. When the crescent is bisected by the first cleavage plane, the smallest cell lies in eighteen percent to the right, and in twenty-nine percent to the left. When the first cleavage plane does not bisect the crescent, the smallest cell lies nearest the centre of the crescent.

XXII. Further researches on the grey substance of the spinal cord

Since the appearance of my second series of investigations on the structure of the Spinal Cord, certain modifications in the method I employ have enabled me to carry my inquiries to a still greater extent, and in many respects beyond the limits of what was actually known on this important subject. By this modified method the elementary nerve-tissues undergo less alteration from their natural state; for the most minute nerve-cells and their processes, as well as the finest fibres, are permanently preserved, and display a sharpness of outline unattainable by any other mode of preparation employed at the present day; while sections the one-twelfth of an inch in thickness may be rendered perfectly transparent. Many of the older anatomists, from Bartholinus downwards, had observed that the grey substance of the spinal cord is softer, more delicate and more vascular than the surrounding white columns; but Rolando was the first to point out a diversity in its structure. He observed, chiefly in quadrupeds, that on each side the posterior third of the grey crescent consists of a peculiar cineritious substance, which presents a different aspect from that which forms its two anterior thirds: it is different in colour, darker, and less red. Rolando, however, assigned too large a space to this "new substance,” which does not comprise so much as the posterior third of the grey crescent, but forms only a comparatively narrow and curved lamina or band around the extremity of each cornu, and, when viewed in a thin section by transmitted light, is found to be actually much paler and more transparent than the rest of the grey crescent. That this lamina is the part indicated by Rolando appears evident on examining his plates.