File:A monograph on the development of elasmobranch fishes (1878) (14765321845).jpg

Identifier: monographondevel00balf (find matches)
Title: A monograph on the development of elasmobranch fishes
Year: 1878 (1870s)
Authors: Balfour, Francis M. (Francis Maitland), 1851-1882
Subjects: Fishes -- Embryology Chondrichthyes
Publisher: London :
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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. Fig. 5. Transverse section through the anterior part of the head of anembryo belonging to stage F. ( x 60 diameters). It shews (1) the ventralcurvature of the medullary folds next the head. (2) The absence ofmesoblast in the anterior part of the head, hy points to the extreme frontend of the aliuientarv canal. Fig. 6. Section tlirough the head of an embryo at a stage intermediatebetween F and G. x 86 diameters. It shews the manner in wliich the medullary folds of the head unite toform the medullary canal. Fig. 7. Longitudinal and vertical section through the tail of an embryobelonging to stage G. It shews the direct communication which exists between the neuraland alimentary canals. The section is not quite parallel to the long axis of the embryo, so thatthe protovertsbrre are cut through in its anterior part, and the neural canalpasses out of the section anteriorly. Fig. 8. Network of nuclei from the yolk of an embryo belonging tostage H. X FlaU A / ^^ J 7 /is, ^ ••/■ J 1- at
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EXPLANATION OF PLATE X. Complete list of reference letters. ep. epiblast df. dorsal fin. sp. c. spinal cord. W. white matter of spinal cord. nc. neural canal. pr. posterior root of spinal nerve. ar. anterior root of spinal nerve. wz^?. muscle-plate. mp. early formed band of muscles from the splanchnic laver of themuscle-plates. Vr. vertebral rudiment. so. somatic laver of mesoblast. sp. splanchnic layer of mesoblast. pp. bodv-cavity, 2K. pericardial cavity. c. connective-tissuecells. sd. segmental duct. st. segmental tube. po. primitive ovum. ao. dorsal aorta. ca v. cardinal vein. .sv. sinus venosus. ht. heart. v. splanchnic vein. ch. notochord. X. subnotochordal rod. al. alimentary tract. sp. v. spiral valve. y. passage connecting the neural and alimentary canals. I hver. p. protoplasm from yolk in the alimentary tract. Fig. 1. Section from the caudal region of a Pristiurus embryo be-longmg to stage H. Zeiss C. Ocul. 1. Osmic acid specimen It shews (1) the constriction of the subnoto

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