On the Impregnation of the Ovum in the Amphibia

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General Books LLC, 2010 - 158 pages
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1851. Excerpt: ... Mammalia, but their evolution has not hitherto been traced, nor their signification been understood. I may now detail the results of an experiment carefully made for the purpose of ascertaining somewhat of their origin and destination; this one will serve as a type of all. On the 27th of March 1853, and at a temperature of 61 Fahr., three eggs were put in a cell and impregnated in the usual way. A single spherical body, projected from the surface of the yelk and maintained for a period at a distance from it on a pedicle, was first noticed "in Lymiueus stagnalis by Carus in 1824 (Von der ausseren Lebensbedingungen der weiss-und kaltbliitigen Thiere, p. 33. t. i. fig. 4), before the investigations of Baer and Purkinje had directed attention to the structure of the ovurn. But this pediculated body was not further regarded by Carus than as the imagined axis of rotation of the yelk. A similar body, but followed also by a second, was also seen in Lymntcus by Dumortier in 1837 (Me-rn. de 1'Acad. de Bruxelles, torn. x. p. 136; also Annales des Sciences Naturelles, 2me seie, torn. viii. 1837, p. 136), and this was immediately supposed by him to be the analogue of the Purkinjean vesicle, and with its fellow, was believed to give origin to the head and foot of the animal. A single body was also noticed in Lymntetts by Pouchet (Sur le de"veloppemeiit de 1'Embryon des Lymne-es, Comptes Rendus, July 1838, pp. 86, 87), and by him likewise was thought to be the Purkinjean vesicle set free from the yelk. But Sars observed two vesicles in Trllonia, Eolis and Doris (wiegmann's Archiv, 1837), and Van Beneden found two in Limax agreslis (muller's Archiv, 1841, p. 180) and Aplysia depilans (Annales des Sc. Nat. torn. xv. p. 126. pi. 1. figs. 4, 7, 9, 1841), and remarked that ...

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