Century Dictionary and Cyclopedia
- n. That larval form of various annelids, mollusks, and mulluscoids which has a circlet of cilia. The trochosphere in Mollusca is an advanced gastrula or gastrular stage of the embryo, prior to the veliger stage, when the original blastopore has been lost or transformed, a rudimentary mouth and anus have appeared, and there is an equatorial circlet of cilia about the spheroidal body. In mollusks also called
- n. zoology A young larval form of many annelids, mollusks, and bryozoans, in which a circle of cilia is developed around the anterior end.
GNU Webster's 1913
- n. (Zoöl.) A young larval form of many annelids, mollusks, and bryozoans, in which a circle of cilia is developed around the anterior end.
- Ancient Greek a wheel + sphere. (Wiktionary)
“The common ancestor alike of unsegmented worms and of all segmented types is probably the trochosphere larva, which in the Vertebrates is represented by the simple _Keimblase_ or blastula.”
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