. The cell in development and inheritance. Cells. CRITIQUE OF THE ROUX-WEISMANN THEORY 307 safe to say that he would never have maintained in the same breath that mitosis is expressly designed for quantitative and also for qual- itative division, had he fixed his attention on the actual phenomena of mitosis alone. The hypothesis is in fact as complete an a priori assumption as any that the history of scholasticism can show, and every fact opposed to it has been met by equally baseless subsidiary hypotheses, which, like their principal, relate to matters beyond the reach of observation. Such an
. The cell in development and inheritance. Cells. CRITIQUE OF THE ROUX-WEISMANN THEORY 307 safe to say that he would never have maintained in the same breath that mitosis is expressly designed for quantitative and also for qual- itative division, had he fixed his attention on the actual phenomena of mitosis alone. The hypothesis is in fact as complete an a priori assumption as any that the history of scholasticism can show, and every fact opposed to it has been met by equally baseless subsidiary hypotheses, which, like their principal, relate to matters beyond the reach of observation. Such an hypothesis cannot be actually overturned by an appeal to fact. When, however, we make such an appeal, the improbability of. A B Fig. 133. — Normal and dwarf gastrulas of Amphioxus. A. Normal gastrula. B. Half-sized dwarf, from an isolated blastomere of the 2-cell stage. C. Quarter-sized dwarf, from an isolated blastomere of the 4-cell stage. the hypothesis becomes so great that it loses all semblance of reality. It is rather remarkable that Roux himself led the way in this direc- tion. In the course of his observations on the development of a half- embryo from one of the blastomeres of the two-cell stage he determined the significant fact that the half-embryo afterivards regenerated the missing Iialf, and gave rise to a complete embryo. Essentiall)' the same result was reached by later observers, both in the frog (Endres, Walter, Morgan) and in a number of other animals, with the impor- tant addition that the half-formation is sometimes characteristic of only the earliest stages and may be entirely suppressed. In 1891 Driesch was able to follow out the development of isolated blasto-. 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 Wilson, Edmund B. (Edmund Beecher), 1856-1939. New York : The Macmillan co
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectcells, bookyear1896
