Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The flat, free-swimming, ciliated larva of a cnidarian.

from The Century Dictionary.

  • noun The ordinary locomotory embryo of the cœlenterates, which is of flattened form, mouthless, ciliate, and free-swimming.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Biol.) In embryonic development, a vesicle filled with fluid, formed from the morula by the divergence of its cells in such a manner as to give rise to a central space, around which the cells arrange themselves as an envelope; an embryonic form intermediate between the morula and gastrula. Sometimes used as synonymous with gastrula.
  • noun (Zoöl.) The very young, free-swimming larva of the cœlenterates. It usually has a flattened oval or oblong form, and is entirely covered with cilia.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun biology In embryonic development, a vesicle filled with fluid, formed from the morula by the divergence of its cells in such a manner as to give rise to a central space, around which the cells arrange themselves as an envelope; an embryonic form intermediate between the morula and gastrula.
  • noun zoology The larva of a hydrozoan, which is free-swimming and covered in cilia.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun the flat ciliated free-swimming larva of hydrozoan coelenterates

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[New Latin plānula, from Latin, feminine diminutive of plānus, flat (from its shape); see pelə- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

Latin, a little plane.

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Examples

  • Some said that the original embryonic form of the metazoa was not the gastrula, but the "planula" -- a double-walled vesicle with closed cavity and without mouth-aperture; the latter was supposed to pierce through gradually.

    The Evolution of Man — Volume 1 Ernst Heinrich Philipp August Haeckel 1876

  • After fertilization, the egg grows into a 'planula' (which is described above as a cilia covered larvae) then finds a spot to temporarily and finishes its last stage of life as a full grown

    CreationWiki - Recent changes [en] 2009

  • He denied that the invagination opening (which he named the blastopore) represented the primitive mouth, [443] holding that this was typically formed by an "inruptive" process at the anterior end of the planula, which led to the formation of a "stomodæum."

    Form and Function A Contribution to the History of Animal Morphology

  • To the fourth stage he assigns the planæa, corresponding to the embryonic development of an albumen and the planula or ciliated {48} larva.

    The Theories of Darwin and Their Relation to Philosophy, Religion, and Morality Rudolf Schmid

  • It was afterwards shown that this planula (found in several sponges, etc.) was a later evolution from the gastrula.

    The Evolution of Man — Volume 1 Ernst Heinrich Philipp August Haeckel 1876

  • The Norwegian Magosphaera planula, swimming about by means of the lashes or cilia at its surface.

    The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

  • Rhopalura Giardi (Julin): Figure 3 male, Figure 4 female, Figure 5 planula.

    The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

  • Section of Magosphaera planula, showing how the pear-shaped cells in the centre of the gelatinous ball are connected by a fibrous process.

    The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

  • The wall of the planula is next pushed in on one side, or invaginated, whereby it is converted into a double-walled sac with an opening, the _blastopore_, which leads into the cavity lined by the inner wall.

    Darwiniana : Essays — Volume 02 Thomas Henry Huxley 1860

  • Each expression pattern is represented by a red shading on the planula, polyp or medusa diagrams.

    PLoS ONE Alerts: New Articles 2009

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