. The cell in development and inheritance. Cells. 352 AXD throui;h()ut the series of living forms, from the lowest to the highest, that it must have a deep significance. And v^hile we are not yet in a position to grasp its full meaning, this contrast points unmistakably to the conclusion that the most essential material handed on by the mother-cell to its progeny is the chromatin, and that this substance therefore has a special significance in inheritance. 4. The Nucleus in Fcj'tilization The foregoing argument receives an overwhelming reenforcement from the
. The cell in development and inheritance. Cells. 352 AXD throui;h()ut the series of living forms, from the lowest to the highest, that it must have a deep significance. And v^hile we are not yet in a position to grasp its full meaning, this contrast points unmistakably to the conclusion that the most essential material handed on by the mother-cell to its progeny is the chromatin, and that this substance therefore has a special significance in inheritance. 4. The Nucleus in Fcj'tilization The foregoing argument receives an overwhelming reenforcement from the facts of fertilization. Although the ovum supplies nearly all the cytoplasm for the embry- onic body, and the spermatozoon at most only a trace, the latter is nevertheless as potent in its effect on the offspring as the former. On the other hand, the nuclei con- tributed by the germ-cells, though apparently different, become in the end exactly equivalent in every visible respect â in structure, in staining-reactions, and in the num- ber and form of the chromosomes to which each gives rise. But furthermore the substance of the two germ-nuclei is distributed with absolute equality, certainly to the first two cells of the embryo, and probably to all later-formed cells. The latter conclusion, which long remained a mere surmise, has been rendered nearly a certainty by the remarkable observations of Riickert, Zoja, and Hacker, de- scribed in Chapters IV. and VI. We must therefore accept the high probability of the conclusion that the specific character of the cell is in the last analysis determined by that of the nucleus, that is by the Fig. and dwarf larva; of the chromatin, and that in the equal sea-urchin. [ ,. ., . ,. , , .â,â,. â â c , . J distribution of paternal and ma- A. Dwarf Pluteus arising from an enucleated _ ^ egg-fragment of Spkcureckhms granular is, fertil- tcmal chromatin tO all the Cclls of ized with spermatozoon of Echinus viicrotiiher- f}
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1906
