Letter | Published:

Sexual Differentiation in Hydra in Relation to Population Density

Naturevolume 191pages9293 (1961) | Download Citation



RECENT reports by Loomis and by Loomis and Lenhoff1 of controlled induction of sexual differentiation in Hydra littoralis have stimulated considerable interest in this process. One of the observations reported is that hydras differentiate sexually in crowded cultures but remain asexual when uncrowded unless the cultures stagnate. This observation is of particular interest because mass cultures of the clone of Hydra littoralis used by Daniel and Park and by Park2 remained continuously asexual for as long as three years. Although culture conditions were considerably different from those described by Loomis, population density and degree of stagnation were apparently comparable.

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  1. 1

    Loomis, W. F., Science, 126, 735 (1957); Sci. Amer., 200, 145 (1959); in Cell, Organism and Millieu, edit. by Rudnick (Ronald Press Co., New York, 1959). Loomis, W. F., and Lenhoff, H. M., J. Exp. Zool., 132, 555 (1956).

  2. 2

    Daniel, George E., and Park, Helen D., J. Cell. and Comp. Physiol., 38, 417 (1951); 42, 359 (1953); Amer. J. Roent., Rad. Ther. and Nuc. Med., 72, 857 (1954). Park, Helen D., Biol. Bull., 111, 240 (1956); Physiol. Zool., 31, 188 (1958).

  3. 3

    Park, Helen D., Anat. Rec., 134, 623 (1959).

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    Present address: National Institute of Dental Research, National Institutes of Health, Bethesda, 14, Maryland


  1. Laboratory of Physical Biology, National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, 14, Maryland



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