INVAGINATION

In‐vag′i‐na″tion (?), n. [[L. pref. in- + vagina sheath.]] 1. 1. (Biol.) The condition of an invaginated organ or part.
2. 2. (Biol.) One of the methods by which the various germinal layers of the ovum are differentiated.
☞ In embolic invagination, one half of the blastosphere is pushed in towards the other half, producing an embryonic form known as a gastrula. — In epibolic invagination, a phenomenon in the development of some invertebrate ova, the epiblast appears to grow over or around the hypoblast.