Definition of "zooid" []

• An organic cell or organized body that has independent movement within a living organism, especially a motile gamete such as a spermatozoon. (noun)
• An independent animallike organism produced asexually, as by budding or fission. (noun)
• One of the distinct individuals forming a colonial animal such as a bryozoan or hydrozoan. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I'm not a biologist, but I do read that a zooid is a single cell that can move independently within a larger organism."
• "It is not easy to imagine two objects more widely different in appearance than a bristle or vibraculum, and an avicularium like the head of a bird; yet they are almost certainly homologous and have been developed from the same common source, namely a zooid with its cell."
• "It is interesting to see two such widely different organs developed from a common origin; and as the moveable lip of the cell serves as a protection to the zooid, there is no difficulty in believing that all the gradations, by which the lip became converted first into the lower mandible of an avicularium and then into an elongated bristle, likewise served as a protection in different ways and under different circumstances."