File:The cell in development and inheritance (1902) (14596676277).jpg

Identifier: cellindevelopmenwils2 (find matches)
Title: The cell in development and inheritance
Year: 1902 (1900s)
Authors: Wilson, Edmund B. (Edmund Beecher), 1856-1939
Subjects: Cell Physiological Phenomena Cells
Publisher: New York : Macmillan
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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e polar bodies are formed (before fertilization). Entering 1 The \.erms fe?)iale pro-jtucleus, male pro-nucletis (Van Beneden), are often appliedto the germ-nuclei before their union. These should, I think, be rejected in favour ofHertwigs terms egg-nucletis and spenn-micleiis, on two grounds: (i) The germ-nuclei aretrue nuclei in every sense, differing from the somatic nuclei only in the reduced number ofchromosomes. As the latter character has recently been shown to be true also of thesomatic nuclei in the sexual generation of plants (p. 275), it cannot be made the ground fora special designation of the germ-nuclei. (2) The germ-nuclei are not male and femalein any proper sense (p. 243). UNION OF THE GERM-CELLS 203 the %g^ 2X any point, the sperm-nucleus first moves rapidly inwardalong an entrance-path that shows no constant relation to the positionof the egg-nucleus and is approximately but never exactly radial,i.e. toward a point near the centre of the &g^. After penetrating a
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Fig. 103. — Diagrams showing the paths of the germ-nuclei in four different eggs of the sea-tirchin, Toxopneustes. From camera drawings of the transparent living eggs. In all the figures the original position of the egg-nucleus (reticulated) is shown at $ ; the pointat which the spermatozoon enters at E (entrance-cone). Arrows indicate the paths traversed bythe nuclei. At the meeting-point (M) the egg-nucleus is dotted. The cleavage-nucleus in itsfinal position is ruled in parallel lines, and through it is drawn the axis of the resulting cleavage-figure. The axis of the egg is indicated by an arrow, the point of which is turned away from themicromere-pole. Plane of first cleavage, passing near the entrance-point, shown by the curveddotted line. certain distance its direction changes slightly to that of the copula-tion-path, which, again, is directed not precisely toward the egg-nucleus, but toward a meeting-point where it comes in contact withthe es:g-nucleus. The latter does not be

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