. The cell in development and inheritance. Cells. PHYSIOLOGICAL RELA7I0NS OF NUCLEUS AND CYTOPLASM 349 in the perivisceral fluid, accompanied by a nurse-cell having a very large chromatic nucleus, while that of the egg is smaller and poorer in chromatin. As the egg completes its growth, the nurse-cell dwindles away and finally perishes (Fig. 'j6^. In all these cases it is scarcely possible to doubt that the egg is in a measure relieved of the task of elaborating cyto- plasmic products by the nurse-cell, and that the great development of the nucleus in the latter is correlated with this functio
. The cell in development and inheritance. Cells. PHYSIOLOGICAL RELA7I0NS OF NUCLEUS AND CYTOPLASM 349 in the perivisceral fluid, accompanied by a nurse-cell having a very large chromatic nucleus, while that of the egg is smaller and poorer in chromatin. As the egg completes its growth, the nurse-cell dwindles away and finally perishes (Fig. 'j6^. In all these cases it is scarcely possible to doubt that the egg is in a measure relieved of the task of elaborating cyto- plasmic products by the nurse-cell, and that the great development of the nucleus in the latter is correlated with this function. Regarding the posi- tion and movements of the nucleus, Korschelt reviews many facts pointing toward the same conclusion. Per- haps the most sugges- tive of these relate to the nucleus of the egg: during its ovarian tory. In many of insects, as in both cases referred to above, the egg-nucleus at first occupies a central posi- tion, but as the Qgg be- gins to grow, it moves to the periphery on the side turned toward the nutritive cells. The same is true in the ovarian eggs of some other animals, good examples of which are afforded by various coelenterates, in medusae (Claus, Hertwig) and actinians (Korschelt, Hertwig), where the germinal vesicle is always near the point of attachment of the Q,gg. Most suggestive of all is the case of the water-beetle Dytis- CHs, in which Korschelt was able to observe the movements and changes of form in the Hving object. The eggs here lie in a single series alter- nating with chambers of nutritive cells. The latter contain granules which are believed by Korschelt to pass into the egg, perhaps bodily, perhaps by dissolving and entering in a liquid form. At all events. his- the the. Fig. 163. — Upper portion of the ovary in the earwig For- Jicula, showing eggs and nurse-cells. [KORSCHELT.] Below, a portion of the nearly ripe egg (e), showing deuto- plasm-spheres and germinal vesicle (). Above it lies the nurse-cell («) with its enorm
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1906
