. A manual of zoology. Zoology. 'j,.ch mm y%i somes, while from tliese poles fi]io threads, the spindle-fibres, run to the centre or equator of the nncleus. These fibres are in many cases certainly derived from the achromatic nuclear reticulum, while in others a greater or less 2)art in their formation is taken by the jirotoplasm. X debated point is the relations of the fibres in the equa- torial plane of the spindle. Do all % the fibres extend from pole to pole ? Do all of them end in the eriuatorial Fig. si.—Spindle formation nnddivi- . ^ . sion of the centrosomes in A>-<:ari» plane, s
. A manual of zoology. Zoology. 'j,.ch mm y%i somes, while from tliese poles fi]io threads, the spindle-fibres, run to the centre or equator of the nncleus. These fibres are in many cases certainly derived from the achromatic nuclear reticulum, while in others a greater or less 2)art in their formation is taken by the jirotoplasm. X debated point is the relations of the fibres in the equa- torial plane of the spindle. Do all % the fibres extend from pole to pole ? Do all of them end in the eriuatorial Fig. si.—Spindle formation nnddivi- . ^ . sion of the centrosomes in A>-<:ari» plane, so that the spindle consists of megalocepliala. (After Brauer.) c, ^ ' i! r-i T centrosomes; c/j. cliromosomes. two cones of fibres separated at the equator ? Or, lastly, are fibres of both kinds present in the same spindle ? It would api)ear that differences exist in these respects in different objects. All of the chromatin of the nucleus lies in the equator, united in the 'equatorial plate,' but by this must not be understood a connected mass but a layer of separate bodies, the chromosomes, for the chromatin of the nucleus divides early into particles which are rarely sj^herical or rodlike, but usually have the shajie of U-shaped loops. Tliese chromosomes are of equal size in the same <-X. Fig. 2:J.—Cell division in the skin of Sutaiiuuidni iiHU'iilnxn. (After Rabl.) cell, and, what is of greater theoretical significance, their num)jer is identical in all the cells of all the tissues of one and the same 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902
