Definition of "planula" []

• The flat, free-swimming, ciliated larva of a coelenterate. (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.

• "Some said that the original embryonic form of the metazoa was not the gastrula, but the "planula" -- a double-walled vesicle with closed cavity and without mouth-aperture; the latter was supposed to pierce through gradually."
• "After fertilization, the egg grows into a 'planula' (which is described above as a cilia covered larvae) then finds a spot to temporarily and finishes its last stage of life as a full grown"
• "To the fourth stage he assigns the planæa, corresponding to the embryonic development of an albumen and the planula or ciliated {48} larva."