The cell in development and inheritance . llar structure, as a rule, onlvduring the mitotic activity of the cell. My own long-continuedstudies on various forms of protoplasm have likewise led to the con-clusion that no universal formula for protoplasmic structure can be 1 For full discussion, with literature list, see Flemming, 82, 97, i, 97, 2, and Biitschli,92, 2, 99. 2 97, I, p. 260. 3 95, 97, 3, gS. 28 GENERAL SKETCH OF THE CELL In that classical object, the echinoderm-egg, for example,it is easy to satisfy oneself, both in the living cell and in sections,that the protoplasm has a
The cell in development and inheritance . llar structure, as a rule, onlvduring the mitotic activity of the cell. My own long-continuedstudies on various forms of protoplasm have likewise led to the con-clusion that no universal formula for protoplasmic structure can be 1 For full discussion, with literature list, see Flemming, 82, 97, i, 97, 2, and Biitschli,92, 2, 99. 2 97, I, p. 260. 3 95, 97, 3, gS. 28 GENERAL SKETCH OF THE CELL In that classical object, the echinoderm-egg, for example,it is easy to satisfy oneself, both in the living cell and in sections,that the protoplasm has a beautiful alveolar structure, exactly asdescribed by Biitschh in the same object (Fig. ii). This structureis here, however, entirely of secondary origin; for its genesis canbe traced step by step during the growth of the ovarian eggs throughthe deposit of minute drops in a homogeneous basis, which ultimatelygives rise to the interalveolar walls. In these same eggs the astralsystems formed during their subsequent division (Fig. 12) are, I. Fig. 12. — Section of sea-urchin egg {Toxopneustes), li minutes after entrance of the sperma-tozoon, showing alveoli and microsomes, sperm-nucleus, middle piece, and aster (about 2000diameters). believe, no less certainly fibrillar; and thus we see the protoplasmof the same cell passing successively through homogeneous, alveolar,and fibrillar phases, at different periods of growth and in differentconditions of physiological activity. There is good reason to regardthis as typical of protoplasm in general. Biitschlis conclusions,based on researches so thorough, prolonged, and ingenious, areentitled to great weight; yet it is impossible to resist the evidencethat fibrillar and granular as well as alveolar structures are of wideoccurrence; and while each may be characteristic of certain kinds of 1 Wilson, 99. STRUCTURAL BASIS OF PROTOPLASM 29 cells, or of certain physiological conditions,^ none is common to allforms of protoplasm. If this positi
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