Sentence Examples


  • If the germcells are differentiated, the offspring arises by syngamy or sexual union of the ordinary type between an ovum and spermatozoon, so-called fertilization of the ovum, or by parthenogenesis, i.e.
  • Development of an ovum without fertilization.
  • The ovum of Hydromedusae is usually one of a large number of odgonia, and grows at the expense of its sister-cells.
  • We may distinguish the following series of stages: (I) ovum; (2) cleavage, leading to formation of a blastula; (3) formation of an inner mass or parenchyma, the future endoderm, by immigration or delamination, leading to the so-called parenchymula-stage; (4) formation of an archenteric cavity, the future coelenteron, by a splitting of the internal parenchyma, and of a blastopore, the future mouth, by perforation at one pole, leading to the gastrula-stage; (5) the outgrowth of tentacles round the mouth (blastopore), leading to the actinula-stage; and (6) the actinula becomes the polyp or medusa in the manner described elsewhere (see articles Hydrozoa, POLYP and Medusa).
  • The cleavage of the ovum follows two types, both seen in Tubularia (Brauer [3]).

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