GLOSSARY 



495 



d is the specific gravity of the granules; p 

 is the specific gravity of the cytoplasm; a 

 is the radius of the granules; n is the coef- 

 ficient of viscosity of the cytoplasm; q is a 

 factor which allows for the fact that there 

 are many granules plus the displacement of 

 cytoplasm in granule movement. 



SUBSTRATE - the substance which is acted upon 

 by an enzyme. 



SUCKER - adhesive, cementing organ of the oral 

 region of anuran larvae. 



SUSCEPTIBILITY, DIFFERENTIAL - evidence 

 of non-homogeneity when diffusely applied 

 injurious agent brings about varying local 

 reactions on the embryo. 



SYMPODIA - fusion, to varying degrees, of the 

 legs {e. g. , mermaid or siren condition!). 



SYNCYTIUM - propagation of nuclei with cyto- 

 plasmic growth but without cytoplasmic 

 division so that there results a mass of 

 protoplasm with many and scattered nuclei 

 but with inadequate cell boundaries (e. g. , 

 chick marginal periblast and adult Nema- 

 todes). 



SYNDACTYLY - either bony fusion or fleshy 



webbing of the digits, generally the second 

 and third digits being involved. Probably 

 inherited in man. 



SYNERESIS - a segregation of the colloidal 

 phases, a corollary of ageing. 



SYNGAMY -fusion of gametes, applied specific- 

 ally to the merging of sperm and egg nuclei. 



SYNOPHTHALMIA - fusion of the eyes as in 

 cyclopia. 



SYNTONIC FACTOR - some regulating force 

 which enables a particular cell to live har- 

 moniously with other cells of the same type 

 so that an organ will develop, not found in 

 tissue cultures of cells isolated prior to 

 differentiation, present during organogene 



SYNTONY - indwelling integration of parts 



(Heidenhain); a natural force within and be- 

 tween cells developing from the specific 

 organization of living matter. 



TACHYAUXESIS - positive heterogony (Need- 

 ham, 1940). 



TACHYGENESIS - speeding up and compression 

 of ancestral stages in development. 



TACTILE DISPLACEMENTS - movements of 

 parts of the embryo relative to each other, 

 resulting in definite formations and distri- 

 butions of the germinal material; evidence 

 of organizational influences. 



TELOBIOSIS - terminal fusion of embryos through 

 operative procedures (see parabiosis). 



TENDENZEN - (German) autonomous abilities 

 of a germ layer to reach developmental 

 capacities as such without the influence of 

 inductive effects (Lehmann, Raven). (See 

 neighborwise and selfwise. ) 



TERATOGENETIC - abnormality producing. 



TERATOLOGY - study of the causes of monster 

 and abnormality formation. 



TERATOMA - structure which results from ran- 

 dom differentiations; malignant assembly of 

 tissues, often well differentiated histolog- 

 ically, generally embedded in an otherwise 

 healthy organ. Some use term embryoma 

 to refer to histological differentiation and 

 teratoma to mean both histological and mor- 

 phological differentiation of the abnormal 

 growth. 



TETRAD - precocious splitting of the chromo- 

 somes in anticipation of both maturation 

 divisions. 



THIXOTROPY - isothermal reversible sol-gel 

 transformations (Fremdlich's monograph). 

 A thixotropic gel will liquefy if shaken or 

 stirred, later to return to its previous con- 

 sistency. 



THORACO-GASTROSCHISIS - failure of the body 

 wall to close along the mid-ventral line, in- 

 cluding the thoracic region. 

 THORACOPAGUS - thoracic union of conjoined 

 twins. 



TISSUE CULTURE - condition where an explant 

 is able to survive and manifest vital activ- 

 ity; in vitro as opposed to in vivo culturing 

 of excised tissues or organs (see isolation 

 culture). 



TOGOGENESIS - all of the processes of move- 

 ment which result in structure formation. 



TOTIPOTENCY - related to theory that the iso- 

 lated blastomere is capable of producing a 

 complete organism. Roux (1912) included 

 several faculties such as (1) for self-differ- 

 entiation; (2) for influencing differentiation 

 or induction of other parts; (3) for specific 

 reaction to differentiating influences as in 

 dependent differentiation. 



TRANSPLANT - an embryonic area (cell or tis- 

 sue) removed to a different environnnent. 

 Syn. , graft. 



TRANSPLANTATION - transfer of an embryonic 

 blastema from one region to another of from 

 one germinal layer to another. Incorporation 

 of an isolated fragment by a living organism, 

 not merely the sticking on of a graft. 



TRANSPLANT, AUTOPLASTIC - exchange of 

 different parts within the same organism. 



TRANSPLANT, HETEROPLASTIC - exchange of 

 parts between individuals of different spe- 

 cies but within the same genus (e. g. , from 

 Amblystoma punctatum to A. tigrinum). 



TRANSPLANT, HETEROTOPIC - graft location 

 different from graft source; exchange made 

 to a non-homologous region of the host; 

 transplantation to a new site. 



TRANSPLANT, HOMOPLASTIC - grafts ex- 

 changed between members of the same spe- 

 cies. Syn. , homoioplastic transplant. 



