Definition of "blastosphere" [blas•to•sphere]

• See blastula. (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.

• "At first the cells present the appearance of a bunch of grapes or the grains of a mulberry, the morula stage; the growth proceeds rapidly, a cavity forms itself inside and the blastosphere stage is reached."
• "We naturally assume, from what we have learnt, that the next stages will be the formation of a hollow blastosphere, invagination, a gastrula forming mesoblast by hollow outgrowths from the archenteron, and so on."
• "The blastosphere of the frog is like what the blastosphere of amphioxus would be, if the future hypoblast cells were enormously larger through their protoplasm being diluted with yolk."