The cell in development and inheritance / by Edmund B. Wilson.

  • Edmund Beecher Wilson
Date:
1902, ©1900
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Licence: Public Domain Mark

Credit: The cell in development and inheritance / by Edmund B. Wilson. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    choplasm or kinoplasm) which is found in the spermatid in the form of a sphere (sometimes an attraction-sphere) or Nebenkern or both. Apart from the nuclear history, these facts have been definitely determined in only a few cases, and much confusion still exists in the accounts of different observers. Thus a number of investigators {e.g. Platner, Field, Benda, Julin, Prenant, Niessing) have asserted that the centrosome passes into the acrosome, instead of Pig. 82. — Formation of the spermatozoon in an insect, Anasa. [Paulmier.] A. Telophase of secondary spermatocyte-division, showing extra chromosome (small dyad of Fig. 127) below. B. Reconstitution of the nuclei. C. Spermatid with Nebenkern (A'') and acrosome {a). D. Nebenkern double, with centrosome between the two halves. E. F. G. Elon- gation of the spermatid, outgrowth of axial filament, migration of acrosome. H. Giant spermatid (double size) with two centrosomes and axial filaments. /. Giant spermatid (quadruple size) with four centrosomes and axial filaments. the middle-piece—^a result which stands in contradiction with the fact that during fertilization in a large number of accurately known cases the centrosome arises from or in immediate relation to the middle- piece (Amphibia, echinoderms, tunicates, annelids, mollusks, insects, etc.; see p. 212). The clearest and most positive evidence on this question, afforded by recent observations on the spermatogenesis of insects, annelids, mollusks. Amphibia, and mammals, leaves, however, little doubt that the former result was an error and that, as the facts