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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1892 edition. Excerpt: ...Holl: Sitzb. Akad. Wiss. Wien, 1890, pp. 311-369, pi. I. These yolk spherules form first near the nucleus and then towards the periphery of the egg. In this way is formed what appears to be the white yolk at the center of the ripe egg. The remaining mass of yolk is made gradually by the conversion of successive layers of granules into yolk spherules. These layers are formed outside the central mass and close to the tunica adventitia, the last formed being the outermost. Some of these layers become converted into yellow yolk. The peripheral granular layer of the egg grows and is nourished by the aid of the zona radiata. This peculiar layer is formed, now, between the tunica adventitia and the granular outermost part of the egg and remains as long as yolk formation continues. Though apparently a part of the ovum, this layer is, the author holds, in reality a system of parallel radiating fibrils which are merely processes of the follicle cells! These processes pass through holes in the tunica adventitia and at the other end become continuous with the meeh-work of the peripheral part of the ovum. The follicle (stroma) cells and the ovum are thus united by intercellular processes, by which nutrient liquids may pass into the ovum. When the egg finally escapes from the ovary some fibrillar remnants of this zona radiata remain adherent to the inner side of the tunica adventitia and thus cause the somewhat double nature of the vitelline membrane. No observations were made upon the proper maturation of the ovum, though certain peculiar bodies in the nucleus are regarded as preparations for the formation of the polar cells. Sexual Glands in Mammals and in the Fowl.1--Dr. J. Janosik, from sections of embryos of the fowl, the sheep, the hog and man, ...

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