. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. \ >J 'C :*V« '^"u THE EFFECTS OF CENTRIFUGING ON THE POLAR SPINDLES OF THE EGG OF CHAETOPTERUS AND CUMINGIA T. H. MORGAN (From the William G. Kcrckhoff Laboratories of the Biological Sciences, California Institute of Technology, Pasadena, California) The factors involved in the movement of the maturation spindle to the pole of the egg are obscure and have been little commented on. In many eggs it has been shown that the mitotic rays may extend through almost the entire polar hemisphere. In such eggs the axis of the s
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. \ >J 'C :*V« '^"u THE EFFECTS OF CENTRIFUGING ON THE POLAR SPINDLES OF THE EGG OF CHAETOPTERUS AND CUMINGIA T. H. MORGAN (From the William G. Kcrckhoff Laboratories of the Biological Sciences, California Institute of Technology, Pasadena, California) The factors involved in the movement of the maturation spindle to the pole of the egg are obscure and have been little commented on. In many eggs it has been shown that the mitotic rays may extend through almost the entire polar hemisphere. In such eggs the axis of the spindle is described as at first horizontal, or possibly somewhat oblique. It then turns with one end directed to the pole, but whether there is one particular end that takes this position or whether either end may so orient is unknown. It is conceivable, if there is a predetermined end, that it may trace back to the last oogonial division, or if not, that a cytoplasmic difference may determine the direction of its turning. At present there is no evidence for either of these assumptions. In some respects the eggs of Chaetopterus offer excellent material for the study of the conditions that lead to the movement of the meiotic spindle to the pole. The eggs can be procured in any quantity, and the same individual will supply material for two or more weeks. When re- moved from the parapodia the germinal vesicle is present in the eggs. It breaks down within a few minutes and the polar spindle forms, which moves within ten minutes to the pole of the egg where it remains until the egg is fertilized. The first polar body is given off 20 to 22 minutes after the egg is fertilized, and the second polar body about ten minutes later. Since all the eggs are in the same stage an opportunity is given to study the effects of centrifuging on the spindle at any stage desired. If the egg is centrifuged at the time when the wall of the germinal vesicle is disappearing, and centrifuging is continued
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
