| 单词 | spiral cleavage |
| 释义 | > as lemmasspiral cleavage b. Zoology in specific names (see quots.). Also spiral cleavage, a pattern of embryogenesis characteristic of certain invertebrate groups, in which the third cell division is asymmetrical and destroys all but four-fold rotational symmetry. ΘΚΠ the world > life > biology > biological processes > procreation or reproduction > embryo or fetus > embryo development processes > [noun] fetalization1819 segmentation1851 maceration1873 neurulation1878 blastulation1889 concrescence1890 cell lineage1892 myelination1892 spiral cleavage1892 medullation1893 myelinization1900 myelogenesis1901 induction1928 myelinogenesis1931 horizon1942 1802 G. Shaw Gen. Zool. III. ii. 564 Spiral Hydrus... Yellowish Hydrus with..spirally contorted body. 1861 P. P. Carpenter in Rep. Smithsonian Inst. 1860 244 Family Limacinidæ. (Spiral Pteropods.) 1892 E. B. Wilson in Jrnl. Morphol. 6 377 The events of the cleavage fall into three very marked periods which I shall designate respectively as the (1) spiral, (2) transitional, and (3) bilateral periods. 1892 E. B. Wilson in Jrnl. Morphol. 6 441 The third spiral cleavage of the primary micromeres gives rise to four apical cells. 1948 New Biol. 5 113 The same fundamental pattern (called spiral cleavage because of the oblique direction of many of the divisions; the actual pattern of cells resulting is not a spiral) is found also in other groups, such as the flatworms. 1967 L. A. Borradaile et al. Invertebrata i. 2 The annelid superphylum has eggs that develop by means of spiral cleavage. When the blastula divides from the four-cell stage to the eight-cell stage the second quartet lie on top of and between the cells of the first quartet. < as lemmas |
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