Egg cleavage
Segmentation Seg`men*ta"tion, n. The act or process of dividing into segments; specifically (Biol.), a self-division into segments as a result of growth; cell cleavage; cell multiplication; endogenous cell formation. [1913 Webster]

{Segmentation cavity} (Biol.), the cavity formed by the arrangement of the cells in segmentation or cleavage of the ovum; the cavity of the blastosphere. In the gastrula stage, the segmentation cavity in which the mesoblast is formed lies between the entoblast and ectoblast. See Illust. of {Invagination}.

{Segmentation nucleus} (Biol.), the body formed by fusion of the male and female pronucleus in an impregnated ovum. See the Note under {Pronucleus}.

{Segmentation of the ovum}, or {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}.

{Segmentation sphere} (Biol.), the blastosphere, or morula. See {Morula}. [1913 Webster]


The Collaborative International Dictionary of English. 2000.

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  • Egg cleavage — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • Egg — ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval or… …   The Collaborative International Dictionary of English

  • Egg and anchor — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • egg and dart — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • egg and tongue — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • Egg development — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • Egg mite — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • Egg parasite — Egg Egg ([e^]g), n. [OE., fr. Icel. egg; akin to AS. [ae]g (whence OE. ey), Sw. [ a]gg, Dan. [ae]g, G. & D. ei, and prob. to OSlav. aje, jaje, L. ovum, Gr. w,o n, Ir. ugh, Gael. ubh, and perh. to L. avis bird. Cf. {Oval}.] 1. (Popularly) The oval …   The Collaborative International Dictionary of English

  • Egg clavage — Cleavage Cleav age, n. 1. The act of cleaving or splitting. [1913 Webster] 2. (Crystallog.) The quality possessed by many crystallized substances of splitting readily in one or more definite directions, in which the cohesive attraction is a… …   The Collaborative International Dictionary of English

  • Cleavage — Cleav age, n. 1. The act of cleaving or splitting. [1913 Webster] 2. (Crystallog.) The quality possessed by many crystallized substances of splitting readily in one or more definite directions, in which the cohesive attraction is a minimum,… …   The Collaborative International Dictionary of English

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