Volume 1

Essays upon heredity and kindred biological problems / by August Weismann ; edited by Edward B. Poulton, Selmar Schönland, and Arthur E. Shipley, authorized translation.

Shipley A. E. (Arthur Everett), Sir, 1861-1927.

Date:: 1891-1892

Credit: Essays upon heredity and kindred biological problems / by August Weismann ; edited by Edward B. Poulton, Selmar Schönland, and Arthur E. Shipley, authorized translation. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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$formed at the anterior part and a new mouth posteriorly. It is not known whether any circulation of the protoplasm takes place, as in Euglypha. But even if this does not occur, there is no reason for believing that the two products of division possess a different duration of life. The process of fission in the Diatomaceae seems to me to be theoretically important, because here, as in the previously- mentioned Monothalamia {Euglypha, etc.), the new siHcious skeleton is built up within the primary organism, but not, as in Euglypha, for the new individual only, but for both parent and daughter-cell alike \ If we compare the diatom shell to a box, then the two halves of the old shell would form two lids, one for each of the products of fission, while a new box is built up afresh for each of them. In this case there is an absolute equality between the products of fission, so far as the shell is concerned. Note ii. Regeneration. A number of experiments have been recently undertaken, in connection with a prize thesis at Wiirzburg, in order to test the powers of regeneration possessed by various animals. In all essential respects the results confirm the statements of the older observers, such as Spallanzani. Carriere has also proved that snails can regenerate not only their horns and eyes, but also part of the head when it has been cut off, although he has shown that Spallanzani's old statement that they can regenerate the whole head, including the nervous system, is erroneous 'K Note 12. The Duration of Life in Plants. The title of the work on this subject mentioned in the Text is ' Die Lebensdauer und Vegetationsweise der Pflanzen, ihre Ursache und ihre Entwicklung,' F. Hildebrand, Engler's bota- nische Jahrbiicher, Bd. II. i. und 2. Heft, Leipzig, 1881. Note 13. [Many interesting facts and conclusions upon the subject of this essay will be found in a volume by Professor E Ray Lankester, ' On comparative Longevity in Man and the lower Animals,' Macmillan & Co., 1870.—E. B. P.] t Cf. Victor Hensen, ' Physiologie d Zeugung,' p. 152. , Cf. ]. Carriere, ' Ueber Regeneration bei Landpultnonaten, iagebl. der 52. Versammlg. deutscher Naturf. pp. 225-226.$