Sentence Examples

  • The unsegmented uterine ovum of P. novae zealandiae measures I.
  • Poulton, showed that the ovum of the platypus was large compared with that of other mammals, whilst W.
  • The result of this is the production of four nuclei, which eventually take up a position at the bottom of the ovum and become separated from one another by vertical cellwalls; these nuclei divide again, and finally three tiers of cells are produced, four in each tier.
  • Regarding the Echinoderms as a whole in the light of the foregoing account, we may give the following analytic summary of the characters that distinguish them from other coelomate animals: They live in salt or brackish water; a primitive bilateral symmetry is still manifest in the right and left divisions of the coelom; the middle coelomic cavities are primitively transformed into two hydrocoels communicating with the exterior indirectly through a duct or ducts of the anterior coelom; stereom, composed of crystalline carbonate of lime, is, with few exceptions, deposited by special amoebocytes in the meshes of a mesodermal stroma, chiefly in the integument; reproductive cells are derived from the endothelium, apparently of the anterior coelom; total segmentation of the ovum produces a coeloblastula and gastrula by invagination; mesenchyme is formed in the segmentation cavity by migration of cells, chiefly from the hypoblast.
  • Development of an ovum without fertilization.