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. 1901 edition. Excerpt: ...and especially where it is beaded (Stentor, Spirostomum, etc.). As a rule the micronuclei are closely attached to the membrane of the macron ucleus, occupying a minute indentation in the latter, but in some cases they are well separated. In form they are round, ellipsoidal, or spindleshaped, but the ...
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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. 1901 edition. Excerpt: ...and especially where it is beaded (Stentor, Spirostomum, etc.). As a rule the micronuclei are closely attached to the membrane of the macron ucleus, occupying a minute indentation in the latter, but in some cases they are well separated. In form they are round, ellipsoidal, or spindleshaped, but the form varies with the nuclear activity, and docs not mean much in itself. Their longest axis measures from 1 n to 10 fi, and like the macronuclei, they are covered with a distinct membrane, while the chromatin is usually massed at some part of the nucleus. In certain cases the appearance is like that of the macronucleus with the chromatin in the form of a densely packed reticulum, giving to it a massive appearance. Here two distinct portions, the chromatin and achromatin, can be made out (Fig. 105). Division of the nuclei takes place by mitosis in the micronuclei, and, as a rule, by amitosis in the macronuclei. The latter is the simpler; in many spherical or elliptical nuclei the structure merely draws out and segments into two equal parts. It is more or less complicated, however, in different macronuclei, until well-developed mitosis replaces simple division (e.g. Spirochona). There is reason to regard the simple division of the larger nuclei as the mere degeneration of mitosis, by a process in which the various stages have gradually disappeared until only the preliminary stages of such division are to be found. These preliminary stages are seen in the transformation of the reticulum of chromatin into thread-like masses, which recall the spireme of Fig. 104.--Loxophyllum mcleagris O. F. M. BALB1ANI. A. Vegetative nuclei with chromatin in the form of a permanent spireme. IS, C, I). The same in division. Fig. 105.--Mitotic division of the nuclei...
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