File:Image from page 638 of "On the anatomy of vertebrates (electronic resource)" (1866) (14755634635).jpg

Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book

Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image: er and more obtuse,fig. 413. The sperrnatoa rarely exceed eight in number in thesperm-cell, from which they usually escape prior to the fulldevelopement and extrication of the spermatozoa. The sameis the case also in Testudo grceca: but here the sperm-cell,fig. 414, a, remains longer than in Lizards and Snakes, andsperrnatoa, ib. b, with developed spermatozoa, may be observedwithin it. § 112. Ovulation in Osseous Fishes and Batrachians. — InCyclostomous and Teleostomous Fishes, and in Batrachians, theova are developed almost simultaneously at each breeding season :whilst in Chimeeroid and Plagiostomous Fishes, as in scaledReptiles, the ova are successively developed, or come to perfectionat longer or shorter intervals. In Osseous Fishes, however,besides the ova of the present season, there are the germs ofthose of the next, often studding the ovisacs of the former. Inthe ovary of the Frog, before pairing-time, three sets of ova are OVULATION IN OSSEOUS FISHES AND BATRACHIANS• 593

Text Appearing After Image: distinguished: those about to be discharged are large and dark-coloured, those intended for the next season are also of uniformsize, but smaller, and partially coloured, and the rest are muchsmaller, colourless, and varying in minuteness. In Plagiostomesthe ova are fewer in number than in the (roe-fish. From fourto fourteen ova, for example, may be developed at one season inthe Torpedo ( T. marmorata)? whilst in the Herring25,000 ova, in the Lump-fish 155,000 ova, in theHolibut, 3,500,000 ova, have been estimated to fillthe enlarged ovarian sacs. In a Lump-fish, thetotal weight of which was 9 lbs. 8 ounces, or 66,500grains, the ovaries weighed 3 lbs. 3 ounces, or 22,300grains : thus they were to the body as 1 to 3. Each °o^cmi?FiSilovum weighed one-seventh of a grain.2 magnified. In all Fishes the ova are formed in chambers of the ovary,called e ovisacs.3 In Osseous Fishes the ovisac consists of adelicate membranous hollow sphere, fig. 415, a, lined byepithelial nucleate ceils, and s

Note About Images