The germ-cell cycle in animals / by Robert W. Hegner.

Date:
1914
Catalogue details

Licence: In copyright

Credit: The germ-cell cycle in animals / by Robert W. Hegner. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the properties of each and a number of properties peculiar to itself. No doubt the protoplasm differs in its physical nature in different cells. In the egg of the starfish, Asterias, Kite (1913) has shown that the cytoplasm is a translucent gel of comparatively high viscosity and is only slightly elastic; pieces become spherical when separated from the rest of the egg. Scattered throughout this gel are minute granules (microsomes) about jjfa mm. in diameter which cannot be entirely freed from the matrix. What appear to be alveoli contain globules which possess many of the optical properties of oil drops; these are suspended in the living gel. The cyto- plasm of the starfish egg is not therefore alveolar in structure as usually stated, but is rather of the nature of a suspension of microsomes and globules in a very viscous gel. The nuclear membrane is a highly translucent, very tough, viscous solid, and not a delicate structure as ordinarily conceived. The nucleolus is a quite rigid, cohesive, granular gel suspended in the sol which makes up the rest of the nuclear material. Dividing male germ cells of cer- tain insects (squash bugs, grasshoppers, and crickets) revealed the fact that the chromosomes are the most highly concentrated and rigid part of the nuclear gel; that the spindle fibers are elastic, concentrated threads of nuclear gel; and that the metaphase spindle fibers seem to be continuous with the ends of the chromosomes. The ground substance of the nucleus is a sol termed nuclear sap or karyolymph. In the so-called ‘rest-