GLOSSARY 1*57 



CACOGENESIS - Inability to hybridize; means "bad descent" (kakogenesis) . 



CAENOGENETIC - term for new stages in ontogeny which have been intercalated as an adaptation to some in- 

 evitable condition which the mode of life of the young animal Imposed ( Baeckel) . 



CALCIUM- RELEASE THEORf - theory of Heilbrunn that the activating agent in parthenogenetic 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. 



CABCINCGEN - a chemical substance which is capable of causing living cells to become cancer-like In growtl. 

 and behavior. 



CABYOLYSIS - solution or dissolution of the nucleus. 



CASYOEHEXIS - breaking up of the nucleus, or its rupture. 



CELL - protoplasmic territory under the control of a single nucleus, whether or not the territory is 



bounded by a discrete membrane. ^ this definition a syncitium is made up of many cells with physio- 

 logical rather than morphological boundaries. 



CELL CHAIN THEORY - theory of neurogenesis wherein the peripheral nerve is of pluricellular origin; op- 

 posed to the outgrowth 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 (syncltial) nuclei or by nuclei migrating 

 from living blastomeres as in the chick blastoderm. 



CELL THEORY - the body of any living organism 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 norphologlcal 

 entity. "Omnis cellula e cellula." Vlrchow 



CENTRIOLE - the granular core of the centrosome, the radiating area comprising the centrosphere. Appears 

 within the centrosome during mitosis, (Conklln). 



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 outlasts the astral 

 rays. Double centrosome called diploaome. 



CENTROSOME, HETEROOTNAMIC - Ziegler's hypothesis that centrosomes may have different powers, thereby 



causing unequal division of the blastomeres such as occurs In many molluscs (e.g., Crepidula) . No 

 evidence of this although there are occasionally size differences In asters of the same spindle 

 complex. 



CEPHALO- THORACOPAGUS - fusion of the head and chest regions in conjoined twins. 



CERVICAL CYST - imperfect occlusion of a branchial (2nd) cleft. Syn., branchial cyst. 



CERVICAL FISTULA - incomplete closure of the branchial cleft. 



CHALONES - Internal secretions with depressing effects, opposed to hormones. 



CHEWO- NEUROTROPISM - chemical attraction of degenerating nerve upon regenerating nerve fibers. The 



chemical nature of nerve orientation (growth and connectlona) depending upon diffusing substances 

 which seem to attract nerve fibers. 



CHIMEEA - compound embryo derived by grafting together major portions of two embryos, generally of dif- 

 ferent species; exchange of parts too great to be called a transplant. From Greek nythology: fore- 

 part a lion, middle a goat, and hlndpart a dragon. 



CHORDA-MESODERM - region of the dorsal lip of the blastopore, arising from the grey crescent area, 

 destined to give rise to notochord and mesoderm In the amphibia. 



CHORIO-ALLANTOIS - a common membrane formed by the fusion of the inner wall of the chorion and the outer 

 wall of the allantois (chick), consisting of outer ectoderm, intermediate fused mesoderm, and inner 

 endoderm. 



CHORIO-ALLANTOIC GRAFT - graft from various sources which, by virtue of Its weight and other factors, 

 provides local irritation of the chorio-allantoic membrane of the chick so that the graft becomes 

 vascularized and surrounded by indifferent tissue, offering the graft excellent conditions for sur- 

 vival, growth, and differentiation. Graft not incorporated by the host from which it receives 

 nutrition for growth. 



CHORION - an embryonic membrane developed in the chick as a corollary to the amnion; encloses both the 

 amnion and the allantois. Never maternal in mammals. 



CHROMATID - longitudinal half of an anaphase. Interphase, or prophase chromosome at mitosis. One of four 

 strands (in melosls) involved in crossing over and visible after pachytene. Becomes a chromosome at 

 metaphase of the second (reduction) division. 



CHROMATIN - deeply staining substance of the nuclear network and the chromosomes, consisting of nucleln; 

 gives Feulgen reaction and stains with basic dyes. 



CHROMATOBLASTS - potential pigment cells which, upon proper extrinsic stimulation, will exhibit pigmen- 

 tation. 



CHROMATOPHORE - pigment bearing cell frequently capable of changing size, shape, and color; responsible 

 for superficial color changes in many animals (e.g., squid £ind chameleon), under the Influence of 

 the sympathetic nervous system and/or the neurohumors. 



CHROMIDIA - extra-nuclear granules of chromatin. 



CHROMONEMA - optically single thread within the chromosome, a purely descriptive term without func- 

 tional implications. 



CHROMONUCLEIC ACID - one of the two types of nucleic acid detected in chromatin only (Polllster & 



Mirsky, 19'+'^). Syn., desoxyribose nucleoproteln, thymonuclelc acid. (See plasmonuclelc acid.) 



CHROMOPHOBE - cells whose constituents are non-stalnable; no affinity for dyes. 



