before a vowel troch-, combining form repr. Gr. τροχός wheel, disk; occurring in several scientific words. Trocheidoscope [after KALEIDOSCOPE], a rotating disk with colored sectors, for showing combinations of colors (Cassell’s Encycl. Dict., 1888). Trochelminth [Gr. ἔλμινς ἑλμινθ- worm], a rotifer. Trochoblast [Gr. βλαστός germ], one of the embryonic cells giving rise to the prototroch in the trochophore larva of marine annelids. Trochocephalic a. [Gr. κεφαλή head], having a round form of skull due to premature union of the parietal and frontal bones; so Trochocephaly, the condition of being trochocephalic. Trochoceracone [Gr. κέρας horn, κῶνος cone], a nautiloid shell with loose flattened coils, as those of the fossil genus Trochoceras; so Trochoceran a., having the form or character of such a shell (Cent. Dict. Suppl.). Trochocœlomate a., belonging to the Trochocœlomata, a proposed division of Metazoa, containing animals having radiated cœlomes (= Radiata). Trochometer [-METER] = TRECHOMETER (Worcester, 1846). Trochophore [Gr. -φόρος bearing], Trochosphere, a larval form constituting a stage in the development of most mollusks and of certain worms, esp. marine annelids, characterized by a spheroidal body with a ring of cilia; also attrib.; hence Trochospheric, -spherical adjs., pertaining to or having the form of a trochosphere. Trochozoon [Gr. ζῷον animal], one of the Trochozoa, a collective name for those mollusks, annelids, etc., which pass through a trochosphere larval stage, or for such larvæ; also for a hypothetical ancestral group of animals from which these are assumed to be derived.
1904. Amer. Nat., July–Aug., 500. Cells … identical in origin with the ‘primary *trochoblasts’ of the annelids.
1878. Bartley, trans. Topinard’s Anthrop., v. 176. *Trochocephalic, very round skull. Ibid., Index 547/1. *Trochocephaly.
1884. Hyatt, in Proc. Boston Soc. Nat. Hist., XXIII. 5 March, 113. We can readily transform a protocoelomate into a *trochocoelomate by destroying the horizontal parts of the partitions between the ampullae in a Sycones.
1892. J. A. Thomson, Outlines Zool., xi. 182. By far the most important larval form among Annelids is that known as the Trochosphere or *Trochophore.
1909. J. W. Jenkinson, Experim. Embryol., 213. Eight instead of the usual four macromeres were found in the Trochophore larva.
1883. E. R. Lankester, in Encycl. Brit., XVI. 648/1. [In the Limpet the] Diblastula … acquires a ciliated band, and becomes a nearly spherical *Trochosphere.
1888. Rolleston & Jackson, Anim. Life, 454. The Mollusca with the exception of Cephalopoda pass through a typical larval development, in two stages—a Trochosphere and a Veliger stage.
1899. Syd. Soc. Lex., *Trochospheric.
1891. Cent. Dict., *Trochospherical.
1890. Nature, 22 May, 94/1. The author’s conclusions are, that the Balanoglossus … has originated from a *trochozoon which acquired some features in common with worms.
