Journal of experimental zoology . presseddown slightly with a cover-glass nosegmentation cavity was found andthe central portion of the egg wasstill unsegmented. The eggs wereexamined at frequent intervals p. M., when the spherules werenot more than half the size ofthose found earlier in the afternoon. Fig. iv. a typical muitispheruiar eggThe next morning no swimming ^^ ^° °^^ f° ^ potassium chiorid br- 1 solution. Camera drawing. Leitz oc. I e found; many were / ^x ^?^? apparently bordering on dissolution and all seemed full of small vacuoles. Sections of these eggs showed that the
Journal of experimental zoology . presseddown slightly with a cover-glass nosegmentation cavity was found andthe central portion of the egg wasstill unsegmented. The eggs wereexamined at frequent intervals p. M., when the spherules werenot more than half the size ofthose found earlier in the afternoon. Fig. iv. a typical muitispheruiar eggThe next morning no swimming ^^ ^° °^^ f° ^ potassium chiorid br- 1 solution. Camera drawing. Leitz oc. I e found; many were / ^x ^?^? apparently bordering on dissolution and all seemed full of small vacuoles. Sections of these eggs showed that the germinal vesicle had broken down in most cases and had diffused out into the cytoplasm before spherulization began. Very infrequently an egg was found with the germinal vesicle intact and surrounded by spherules. There was never any mitotic division of the nucleus. In eggs where the nuclear sap diffused out into the cytoplasm, there was found a more or less diffuse achromatin stain in each spherule. It is very evident that. 68 John W. Scott this peculiar change in some eggs is not one of differentiation,but is due to the effect of the potassium chlorid in altering theviscosity and lowering the surface tension of the the spherulization continues for some hours after it begins,it seems that the cytoplasm may undergo a ripening process,somewhat as the normal egg must do in order that cleavage intosmall cells may occur; and inasmuch at the process of spheruliza-tion continues longer in eggs where the germinal vesicle has pre-viously broken down, it indicates that the diffused nuclear sapmay have something to do with this ripening process. Treadwell(02) when working upon Podarke noticed that some of the controleggs broke up into a great many small globules with no traceof nuclear division, the nucleus lying in one cell which was usuallylarger than the others. He found no ciliated embryos amongthese eggs. 3. Description of Swimming Embryos, Eighteen to Twenty-f
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1904
