Le Volvox

    Abstract

    IN this third memoir M. Janet approaches the problem of the ontogenesis of the Volvox blastea (ccenobium). He confines himself to the methods of cell bipartition, but in later works he proposes to discuss variations in the process and special cases. The memoir is an able attack on an exceedingly intricate and difficult problem and contains a wealth of minute detail. The author starts by pointing out the primitiveness of the Volvox cell and how, in his opinion, these blasteas are in large measure representative of the primitive animal cell groups. He then goes on to describe the apparatus by means of which he separates out the minute organisms, and having pointed out the fundamental units of the cell he considers the homologies between the blasteas of plants and animals. Thereafter he examines the divisions of the cells of Janetosphcgra aurea (Ehrbg.) Shaw, in greater detail. It can be well understood that in such an involved study a comprehensive scheme of terms is required; these the author has supplied as well as formulae for expressing symbolically the type of generation and the mode of reproduction of the organism under study. Assisted by 21 excellent plates containing many figures and diagrams, he traces the various divisions and shows that after bipartitions resulting in 1024 cells, the cells of J. aurea, having reached their minimum limits and used up all available reserves, cease to divide and enter into a new phase-the flagellate stage. Throughout, the work is one where questions regarding evolution in the plant world are always kept to the front, for the author's knowledge of plant and animal life permits him to make useful comparisons.

    Le Volvox.

    Charles

    Janet

    Par. Troisième mémoire: Ontogénèse de la blastéa volvocéenne. Première partie. Pp. 179+planches 5–21. (Macon: Protat frères, 1923.) n.p.

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    Le Volvox . Nature 115, 11 (1925) doi:10.1038/115011b0

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