Wiktionary
trochophore
n. (context biology English) The free-swimming larva of some invertebrates that have a circlet of cilia
Wikipedia
Trochophore
A trochophore (; also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia.
By moving their cilia rapidly, a water eddy is created. In this way they control the direction of their movement. Additionally, in this way they bring their food closer, in order to capture it more easily.