‖ planula Zool.
(ˈplænjʊlə)
Pl. -æ.
[mod.L., a little plane, dim. of plānus plane a.]
The flat-shaped ciliated free-swimming embryo of certain Hydrozoa; hence extended to a similar embryo in Cœlenterates generally.
| 1870 Nicholson Man. Zool. 89 The embryo is a free-swimming, oblong, ciliated body, termed a planula. 1877 Huxley Anat. Inv. Anim. iii. 146 In most Hydrophora the ciliated, locomotive, planula becomes elongated and fixed by its aboral pole. 1878 Bell Gegenbaur's Comp. Anat. 98 Developed, just like the Hydroid-Polyps, from a planula, which is at first free, and which afterwards becomes fixed. |
| attrib. 1887 Sollas in Encycl. Brit. XXII. 425/2 The history of the second or planula type [of development] has been thoroughly worked out by Schulze in a little incrusting Tetractinellid sponge (Plakina monolopha, Schulze). |
So
ˈplanulan, a planula;
ˈplanular a., (
a) of flattened form; (
b) pertaining to or of the nature of a planula;
ˈplanulate a., of a flattened form;
ˈplanuliform a., of the form of a planula;
ˈplanuloid a., resembling a planula.
| 1886 Geddes in Encycl. Brit. XX. 420/2 The passage from Protozoa to Metazoa was, according to Bütschli, effected neither by *planulan nor gastrula but by a disk-like ‘placula’. |
| 1858 Mayne Expos. Lex., Planularis, applied by Lamarck to a section (Planulares) of soft worms having flat bodies: *planular. 1895 Syd. Soc. Lex., Planular, pertaining to a Planula. |
| 1846 Dana Zooph. (1848) 570 The cells are nearly circular, contiguous, or *planulate. |
| 1877 Huxley Anat. Inv. Anim. viii. 459 In the fresh-water Polyzoa, the impregnated ovum gives rise to a saccular *planuliform embryo. |
| 1895 Syd. Soc. Lex., *Planuloid, the same as Planuliform. |