Egg cleavage


  • Webster's Revised Unabridged Dictionary
    • Egg cleavage (Biol) a process of cleavage or segmentation, by which the egg undergoes endogenous division with formation of a mass of nearly similar cells, from the growth and differentiation of which the new organism is ultimately formed. See Segmentation of the ovum, under Segmentation.
    • Egg cleavage (Biol) the process by which the embryos of all the higher plants and animals are derived from the germ cell. In the simplest case, that of small ova destitute of food yolk, the ovum or egg divides into two similar halves or segments (blastomeres), each of these again divides into two, and so on, thus giving rise to a mass of cells (mulberry mass, or morula), all equal and similar, from the growth and development of which the future animal is to be formed. This constitutes regular segmentation. Quite frequently, however, the equality and regularity of cleavage is interfered with by the presence of food yolk, from which results unequal segmentation. See Holoblastic Meroblastic Alecithal Centrolecithal Ectolecithal, and Ovum.
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In literature:

Segmentation of egg: the division of the originally single celled egg into a number of coherent cells or blastomeres; = cleavage.
"Explanation of Terms Used in Entomology" by John. B. Smith
In these cases heteromorphosis begins from the first cleavage of the egg.
"The Biological Problem of To-day" by Oscar Hertwig
In ten eggs (KU 62154 from San Salvador, El Salvador) the average diameter of the embryos in first cleavage is 1.3 mm.
"Neotropical Hylid Frogs, Genus Smilisca" by William E. Duellman
In such eggs the first cleavage spindle is four-poled.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8" by Various
CLEAVAGE, the division of the egg-cell into many cells.
"Being Well-Born" by Michael F. Guyer