. The Protozoa. Protozoa. Fig. 139. — Mitotic division in the Infusoria. [From Wilson after R. Hertwig.] A-C. Macronucleus of Spirochona, showing pole-plates. D-H. Successive stages in the divi- sion of the micronucleus of Paramcecium. D. The earliest stage, showing reticulum. G. Follow- ing stage ("sickle-form") with nucleus. E. Chromosomes and pole-plates. F. Late anaphase. H. Final phase. in which the origin of the pole-plates has been definitely made out. In all cases, however, it is assumed that the so-called nucleolus or "achromatic body," which is generally present i
. The Protozoa. Protozoa. Fig. 139. — Mitotic division in the Infusoria. [From Wilson after R. Hertwig.] A-C. Macronucleus of Spirochona, showing pole-plates. D-H. Successive stages in the divi- sion of the micronucleus of Paramcecium. D. The earliest stage, showing reticulum. G. Follow- ing stage ("sickle-form") with nucleus. E. Chromosomes and pole-plates. F. Late anaphase. H. Final phase. in which the origin of the pole-plates has been definitely made out. In all cases, however, it is assumed that the so-called nucleolus or "achromatic body," which is generally present in the resting cell- nucleus, becomes modified in some manner (Hertwig, '95, assumed by the addition of water or other fluid substance) until it is much en- larged, when it forms the pole-plates. This general view is based upon the supposition that, like a centrosome, the achromatic body divides, half going to one pole and half to the other. In Sarcodina, as in Infusoria, there is no direct evidence to de- termine the history of the "achromatic" body within the nucleus,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Calkins, Gary N. (Gary Nathan), b. 1869. New York, The Macmillan company; London, Mamcillan & co. , ltd.
Size: 2810px × 890px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcalkinsg, bookcentury1900, bookdecade1900, bookyear1901
