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GLOSSARY 



BLASTOPORE, DORSAL LIP OF - the region 

 of initial involution of cells in the amphib- 

 ian or chick gastrula; general area of the 

 "organizer"; original grey crescent area 

 of many amphibia; the cells which turn in 

 beneath the potential central nervous sys- 

 tem (Amphioxus) and form the roof of the 

 archenteron (urodela). Syn. , germ ring 

 or marginal zone. 

 BLASTOPORE, VENTRAL LIP OF - region of 

 the germ ring opposite the dorsal lip after 

 involution has reached this point; region 

 which gives rise to the peristomial meso- 

 derm of the frog. Syn. , germ ring. (Note: 

 The lips of the blastopore are continuous 

 and represent the involuted germ ring. ) 



BLASTOTOMY - separation of cells or groups 

 of cells of the blastula, by any means. 



BLASTULA - a stage in embryonic development 

 between the appearance of distinct blasto- 

 meres and the end of cleavage (i. e. , the 

 beginning of gastrulation); a stage generally 

 possessing a primary embryonic cavity or 

 vesicle known as the blastocoel; invariably 

 monodermic, although the roof may be 

 multi -layered. 



BLOOD ISLANDS - pre-vascular groups of 



mesodermal cells found in the splanchno- 

 pleure, from which arise the blood vessels 

 and corpuscles. Generally extra-embry- 

 onic (chick). 



BOTTLE CELLS - long-necked, cylindrical 

 cells of the blastoporal lips (amphibia) 

 whose function may be purely morphogen- 

 etic and related to the involutionary proc- 

 esses of gastrulation, (Holtfreter, 1943). 

 Ruffini (1925) showed that flask-shaped 

 cells appear wherever infoldings occur, as 

 in the formation of the neural tube, eye 

 vesicle, nasal placode, stomodeum, procto- 

 deum, etc. These cells are held together 

 by strands of surface coating. 



BRADYAUXESIS - negative heterogony (Need- 

 ham &t Lerner, 1940), the part grows more 

 slowly than the whole. 



BRADYGENESIS - lengthening of certain stages 

 in development. 



BRANCHIAL - having to do with respiration 

 (e. g. , branchial vessel in gill). 



BRANCHIOMERY - type of metamerism exem- 

 plified in the visceral arches. 



BRYSHTHALMIA - eyes that are too large, may 

 be due to oversized lenses. 



BUD - an undeveloped branch, generally an 



anlage of an appendage (e. g. , limb or wing 

 bud). 



BUPHTHALMIA - eyes that are too large 

 (Harrison, 1929). 



CACOGENESIS - inability to hybridize; means 

 "bad descent" (kakogenesis). 



CAENOGENETIC - term for new stages in on- 

 togeny which have been intercalated as an 



adaptation to some inevitable condition 

 which the mode of life of the young animal 

 imposed (Haeckel). 



CALCIUM-RELEASE THEORY - theory of 



Heilbrunn that the activating agent in par- 

 thenogenetic stimulation releases calcium 

 from calcium proteinate in the cell cortex, 

 and the free calcium then brings about a 

 protoplasmic clotting necessary to the 

 initiation of development. 



CARCINOGEN - a chemical substance which is 

 capable of causing living cells to become 

 cancer-like in growth and behavior. 



CARYOLYSIS - solution or dissolution of the 

 nucleus. 



CARYORHEXIS - breaking up of the nucleus, 

 or its rupture. 



CELL - protoplasmic territory under the con- 

 trol of a single nucleus, whether or not the 

 territory is bounded by a discrete mem- 

 brane. By this definition a syncitium is 

 made up of many cells with physiological 

 rather than morphological boundaries. 



CELL CHAIN THEORY - theory of neurogen- 

 esis wherein the peripheral nerve is of 

 pluricellular origin; opposed to the out- 

 growth theory. 



CELL-CONE - a sub-system of an ordered 

 class of cells; a single cell (other than a 

 zygote) and all cells derived from it in a 

 division heirarchy. 



CELL LINEAGE - the study of the origin and 



fate of specific cells (blastomeres) in early 

 embryonic development. Syn. , cytogeny. 



CELLULATION - development of cytoplasmic 

 areas around normal (syncitial) nuclei or 

 by nuclei migrating from living blastomeres 

 as in the chick blastoderm. 



CELL THEORY - the body of any living organ- 

 ism is either a structural and functional 

 unit or is composed of a nucleus and its 

 sphere of influence, whether or not that 

 sphere is bounded by a morphological entity. 

 "Omnis cellula e cellula. " Virchow 



CENTRIOLE - the granular core of the centro- 

 some, the radiating area comprising the 

 centrosphere. Appears within the centro- 

 some during mitosis. (Conklin). 



CENTROSOME - the dynamic center involved in 

 mitosis, including the central granule 

 (centriole) and the surrounding sphere of 

 rays (centrosphere). It is the center of the 

 aster which cmtlasts the astral rays. 

 Double centrosome called diplosome. 



CENTROSOME, HETERODYNAMIC - Ziegler's 

 hypothesis that centrosomes may have dif- 

 ferent powers, thereby causing unequal 

 division of the blastomeres such as occurs 

 in many molluscs (e. g. , Crepidula). No 

 evidence of this although there are occa- 

 sionally size differences in asters of the 

 same spindle complex. 



CEPHALO-THORACOPAGUS - fusion of the head 

 and chest regions in conjoined twins. 



