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

  • Edmund Beecher Wilson
Date:
1902, ©1900
Catalogue details

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.

    201/522 (page 173)
    This tallies with Strasburger's earlier conclusion that the cilia-bearing region consists of kinoplasm and corresponds to the middle-piece ('92, p. 139), but gives a still more definite basis of comparison.-^ The history of the centrosome-like bodies {blepJiaroplasts of Web- ber, '97, 3) has been carefully followed out in Zaniia and Gingko by Webber ('97), and in Cycas by Ikeno ('97, '98) with nearly similar results. In all these forms (Fig. 87) the blepharoplasts appear in the Fig. 87. — Formation of the spermatozoids in the cycads. \_A, GiNGKO; B-D, Zamia, Webber; E-I, Cycas, Ikeno.] A. Developing pollen-tube, showing stalk-cell (j), vegetative cell {v) and generative cell {g), the latter with two blepharoplasts. B. Generative cell, somewhat later, with blepharoplasts and asters. C. The same in the prophases of division, showing breaking up of blepharoplasts. D. The two spermatids formed by division of the generative cell; blepharoplasts fragmented; from these fragments arises the cilia-bearing band. E. Blepharoplast of Cycas, at a stage some- what later than Fig. C\ cilia developing. F. Later stage; ciliated band (derived from the last stage) attached to a prolongation from the nucleus. G. Cilia-bearing band continuous. H. Nearly ripe spermatozoid with nucleus in the centre; ciliated band, shown in section, forming a spiral. /. Slightly later stage, viewed from above, showing the spiral course of the band (cilia omitted). penultimate cell-generation lying one on either side the nucleus, and in earlier stages surrounded by astral radiations very closely resem- bling those of a typical mitotic aster, and they lie opposite the poles ^ The anterior region of the spermatozoid thus corresponds to the posterior region of the spermatozoon, the confusion of terms having arisen from the fact that the former swims with the cilia-bearing region in front, the latter with the flagellum directed backward.