Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- n. The flat, free-swimming, ciliated larva of a coelenterate.
Century Dictionary and Cyclopedia
- n. The ordinary locomotory embryo of the cœlenterates, which is of flattened form, mouthless, ciliate, and free-swimming. The term originally applied only to such embryos of certain hydrozoans, but has become more comprehensive. See cut under
blastocœle .
Wiktionary
- n. 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.
- n. zoology The larva of a hydrozoan, which is free-swimming and covered in cilia.
GNU Webster's 1913
- n. (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 . - n. (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.
WordNet 3.0
- n. the flat ciliated free-swimming larva of hydrozoan coelenterates
Etymologies
- Latin, a little plane. (Wiktionary)
- New Latin plānula, from Latin, feminine diminutive of plānus, flat (from its shape); see pelə-2 in Indo-European roots. (American Heritage® Dictionary of the English Language, Fourth Edition)
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.”
“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”
“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
“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
“The Norwegian Magosphaera planula, swimming about by means of the lashes or cilia at its surface.”
“Rhopalura Giardi (Julin): Figure 3 male, Figure 4 female, Figure 5 planula.”
“Section of Magosphaera planula, showing how the pear-shaped cells in the centre of the gelatinous ball are connected by a fibrous process.”
“It was afterwards shown that this planula (found in several sponges, etc.) was a later evolution from the gastrula.”
“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.”
“Each expression pattern is represented by a red shading on the planula, polyp or medusa diagrams.”
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colt, foal, kitten, cub, pup, heifer, larva, imago, veliger, trochophore, grub, maggot and 178 more...
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