. A manual of zoology. Zoology. 5S GENERAL PRINCIPLES OF ZOOLOGY nucleoli (true or chromatiu-frce nucleoli"), while the chromatin is ciis- tributed on the nuclear reticulum (chromatin reticulum). INIuch the same may occur in the Protozoa (tig. 19, 3). Beside and outside of the nucleus there occurs in many Protozoa a 'cliroDiiil- ial apparalus,' a substance agreeing in its staining properties with the nuclear substance. Its pertinence to the nucleus is also shown by the fact that repeatedly it has been observed to arise from the nucleus (Ac/iiiosplurriinii), as well as to be transformed in
. A manual of zoology. Zoology. 5S GENERAL PRINCIPLES OF ZOOLOGY nucleoli (true or chromatiu-frce nucleoli"), while the chromatin is ciis- tributed on the nuclear reticulum (chromatin reticulum). INIuch the same may occur in the Protozoa (tig. 19, 3). Beside and outside of the nucleus there occurs in many Protozoa a 'cliroDiiil- ial apparalus,' a substance agreeing in its staining properties with the nuclear substance. Its pertinence to the nucleus is also shown by the fact that repeatedly it has been observed to arise from the nucleus (Ac/iiiosplurriinii), as well as to be transformed into nuclei (Radiolaria, jNlonothalamia). The chronu'diai mass may surround the nucleus like a cortical layer (Eiiglyplia, tig. 20, III, Radiolaria), or pienetrate the protoplasm as a loose network (II), or form Ium]is or coiled threads. In this last shape the chroraidial mass seems to be widely distributed in strongly functioning cells of Melazoa (I). Possibly the structures described as ' iiiilocliondria' are identical witli Fig. 20.—Cells with chromidial apparatus. I, muscle cell of A scar is (after Goldschmidt). II, Arcclla, with two nuclei and loose chromidial net. Ill, Eiiglyplia with compact chromidial envelope of the nucleus, fit, chroniidial mass;_/, food bo<,h'; m, mouth of shell; », nucleus; r, reserve material for new shell. Function of the Nucleus.—For a long time the function of the nucleus in the cell was shrouded in complete darluicss, so that it was regarded, in comparison with the protoplasm, as of little importance. The evidence that the nucleus plays the most prominent role in fertilizatioii has altered this conception. Then arose the view that the nucleus deter- mines the character of the cell; that the potentiality of the protoplasm is influenced by the nucleus. If front the egg a definite kind of animal develop, if a cell in the animal's hotly assume a dehnite histological character, we are, at the present time, inclined to ascrilic this to the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
