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Show 272 MR. F. E. BEDDARD ON THE [May 4, 2. Observations on the Ovarian Ovum of Lepidosiren (Pro-topterus). By F R A N K E. B E D D A R D , M.A., F.R.S.E., Prosector to the Society. [Received M a y 3, 1886.] (Plates XXVIII. & XXIX.) I. Introduction, p. 272. II. Egg-membranes, p. 273. III. Germinal Vesicle, p. 276. IV. Follicular Epithelium and Development of Yolk, p. 279. V. Postembryonic Origin of Ova, p. 288. VI. Resume, p. 291. I. Introduction. A recent memoir on the anatomy of the Dipnoi by Howard Ayers ] contains some account of the ovaries and the ova in Lepidosiren2, illustrated by several figures. The description of these organs is, however, mainly anatomical; and though in the figures some histological details of the ovary and the contained ova are to be found, their structure is not described. The author contents himself with remarking upon the similarity to the Amphibia, and all that I can find in his paper about the minute structure of the ovaries and ova is the following paragraph 3 :-" Die Structur der Eierstbcke ist direkt vergleichbar mit der der Urodelen. Die ver-schiedenen Stadien in der Entwickelung der Eier aus dem Keimepithel sind, soweit bei dem in Alcohol konservirten Material festgestellt werden konnte, wesentlich dieselben, wie sie fiir niedere Wirbelthiere constatirt sind. Wenn die Eier vollig entwickelt sind, so ist eine Halfte ihrer Oberflache pigmentirt (diejenige, welche gegen die freie Halfte des Eierstockes gerichtet ist), wahrend die andere Halfte farblos bleibt"4. Furthermore, in describing the anatomical relations of the different parts of the genital system, Dr. Ayers takes occasion to remark that the sexual cells (both ovaries and testes) are inclosed in two delicate sacs-an outer peritoneal, and an inner formed by the connective-tissue stroma. I shall refer more particularly to the appearances depicted in Ayers's figures in considering the structure of the ovaries and ova as I interpret them from my own preparations. 1 "Beitrage zur Anatomie und Physiologie der Dipnoer," Jenaische Zeitschr. vol. xviii. (1885), pp. 479-527, 3 plates. 2 The specimen studied by myself is from the Nile, and would therefore, according to some authors, be more properly termed Protopterus. Dr. Ayers shows reasons for assuming that there is really no generic distinction between the American Lepidosiren and the African Protopterus; the former name should therefore, on grounds of priority, be retained. 3 Loc. cit. p. 508. 4 This is a curious point of similarity to the ova of the Frog (see Balfour Oomp. Embr. vol. ii. p. 99; Pfluger, Arch. f. d. ges. Physiol. Bd. xxxi. 1883)^ not remarked upon by Ayers in his paper. |
