. The cell in development and inheritance. Cells; Cells. PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 255 ,f^i. of such cells at one pole of the egg from which the latter is believed to draw its nutriment (Fig. 58). A very interesting case is that of the annelid OphryotrocJia, referred to at p. 114. Here, as described by Korschelt, the ^gg floats in the perivisceral fluid, accompanied by a nurse-cell having a very large chromatic nucleus, while that of the &gg is smaller and poorer in chromatin. As the completes its growth, the nurse- cell dwindles away and finally perishes (Fig.
. The cell in development and inheritance. Cells; Cells. PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 255 ,f^i. of such cells at one pole of the egg from which the latter is believed to draw its nutriment (Fig. 58). A very interesting case is that of the annelid OphryotrocJia, referred to at p. 114. Here, as described by Korschelt, the ^gg floats in the perivisceral fluid, accompanied by a nurse-cell having a very large chromatic nucleus, while that of the &gg is smaller and poorer in chromatin. As the completes its growth, the nurse- cell dwindles away and finally perishes (Fig. 57). In all these cases it is scarcely possible to doubt that the is in a measure relieved /^V-'. i<:.. n of the task of elaborat- ing cytoplasmic products by the nurse-cell, and that the great develop- ment 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 towards the same conclusion. Per- g 1' haps the most sugges- tive of these relate to the nucleus of the o^gg. during its ovarian his- tory. In many of the insects, as in both the Fig. 115. — Upper portion oi the ovary in the earwig Fofjiciila, showing eggs and nurse-cells. [KORSCHELT.] Below, a portion of the nearly ripe egg {e), showing deuto- plasm-spheres and germinal vesicle {gv). Above it lies the nurse-L-ell {ti) with its enormous bi'anching nucleus. Two cases referred to above si^ii^cessively younger stages of egg and nurse are shown above. the egg-nucleus at first occupies a central position, but as the egg bsgins to grow, it moves to the periphery on the side turned towards 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 tgg. Most suggestive of all is the case of the wa
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectcells, bookyear1896
