• WordNet 3.6
    • n invagination the folding in of an outer layer so as to form a pocket in the surface "the invagination of the blastula"
    • n invagination the condition of being folded inward or sheathed
    • ***
Webster's Revised Unabridged Dictionary
    • Invagination (Biol) The condition of an invaginated organ or part.
    • Invagination (Biol., Embryology) The inward movement of one part of the wall of a blastula, to form a gastrula; the process of gastrulation, in which layers of the ovum are differentiated.
    • Invagination The inward movement of the wall of a tissue or cell, to form a cavity; also, the cavity thus formed.
    • ***
Century Dictionary and Cyclopedia
    • n invagination The act of introverting or sheathing, or the state of being sheathed; insertion or reception as into a sheath; intussusception.
    • ***
Chambers's Twentieth Century Dictionary
    • n Invagination in-vaj-i-nā′shun intussusception.
    • ***


Webster's Revised Unabridged Dictionary
L. pref. in-, + vagina, sheath
Chambers's Twentieth Century Dictionary
L. in, not, vagina, a sheath.


In literature:

The gastrula, finally, is the two-layered sac formed from the blastula, typically by invagination of its wall.
"Form and Function" by E. S. (Edward Stuart) Russell
Invagination follows (Figure 6).
"Text Book of Biology, Part 1: Vertebrata" by H. G. Wells
No sign of a cloacal invagination could be made out with certainty.
"Development of the Digestive Canal of the American Alligator" by Albert M. Reese
Invaginate: when a tubular or vesicular part is turned inward or retracted within the body wall.
"Explanation of Terms Used in Entomology" by John. B. Smith
Unless the invaginated portion of the gut becomes strangulated, probably no symptoms except constipation will be appreciable.
"Special Report on Diseases of the Horse" by United States Department of Agriculture
This action will stand for the process of invagination.
"Essays: Scientific, Political, & Speculative, Vol. I" by Herbert Spencer
"Special Report on Diseases of Cattle" by U.S. Department of Agriculture
It results from this arrangement that the cells forming all but the bottom of the invagination lie horizontally, i.e.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 6" by Various
The segmentation is complete; one side of the hollow blastosphere invaginates and forms a gastrula.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7" by Various
In other Arthropods the cerebral ganglia arise in a similar way, but the invaginations disappear in the adult.
"Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3" by Various
The invagination above the diaphragm, consisting of both endocyst and ectocyst, is then everted.
"Freshwater Sponges, Hydroids & Polyzoa" by Nelson Annandale
Local conditions of growth cause the invagination of a set of the cells of the blastosphere-wall.
"The Biological Problem of To-day" by Oscar Hertwig
Eyes are open invaginations without crystalline lens.
"Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5" by Various
In some cases the invaginated gut may be felt protruding through the sphincter.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 6" by Various
The germ-layer formation is always by immigration or delamination, never by invagination.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2" by Various
At the narrow end an invagination takes place, which gives rise to an open sac, the blind end of which is directed forwards.
"The Works of Francis Maitland Balfour, Volume 1" by Francis Maitland Balfour