494 



GLOSSARY 



SELBSTORGANIZATION - invisible process of 

 construction and reconstruction of a normal 

 blastema, with its quantitative organization 

 gradient which is itself the basis for the 

 segregation from qualitatively differing 

 organ-forming regions. 



SELF-DIFFERENTIATING CAPACITY - the 



capacity of a part of a developing system to 

 pursue a specific course. The characters 

 of that course are determined by intrinsic 

 properties of the part (Roux, 1881). There 

 can be no self-differentiation without prior 

 induction. (See differentiation, self. ) 



SELF -ORGANIZATION - obsolete term which 



meant the alleged appearance of a lens with- 

 out the stimulus normally coming from the 

 optic cup (see double assurance). 



SELFWISE - behavior of a transplant in a man- 

 ner expected in its original environment, in 

 accordance with its normal prospective sig- 

 nificance. 



SENESCENCE - the progressive loss of growth 

 power; old age. 



SENSITIZATION THEORY - calcium is the true 

 activating agent in artificial parthenogenesis 

 and other substances increase the perme- 

 ability of the egg cortex to calcium (Pas- 

 teels). 



SENSORY LOAD - determined by the number of 

 receptor organs associated with a specific 

 nerve. 



SEX, HETERODYNAMIC - the sex in which the 

 gametes are of two kinds with respect to 

 the possession of specific sex influencing 

 chromosomes, such as the X-chromosome 

 in Drosophila. The frog and human male 

 are presumably heterogametic. 



SIGNIFICANCE, PROSPECTIVE - actual fate of 

 any part of the original egg. Syn. , Driesch's 

 "prospektive Bedeutung". 



SITUS INVERSUS - an inversion of the bilateral 

 symmetry; reversal of right and left sym- 

 metry. 



SITUS INVERSUS VISCERUM - twisting of the 

 digestive tract and sometimes the heart, 

 occurring naturally (rarely) or as a result 

 of shifting of embryonic parts (Spemann, 

 1906) as in reversing a square piece of pre- 

 sumptive neural plate and archenteron of 

 the early gastrula. 



SOL - a colloidal system in which the particles 

 of a solid or of a second liquid are sus- 

 pended in a continuous phase of a liquid, the 

 particles or their aggregates being too large 

 to go through animal membranes rapidly or 

 at all. 



SOMATIC DOUBLING - doubling of the initial 

 nunnber of chromosomes with which the egg 

 begins development, occurring (probably in 

 most cases) at the first or early mitotic 

 divisions (cleavages) of the egg. after fer- 

 tilization. 



SOMATOBLAST - blastomere with specific germ 

 layer predisposition such as actodermal 

 somatoblasts. 



SPALTUNG - (German) fusion of posterior neural 

 axes in a twin embryo, simulating an induc- 

 tion. 



SPECIFICITY - the summation of the cytochem- 

 ical characteristics of different protoplasms 

 (Humphrey and Burns, 1939). 



SPERMOPHILE GROUP - portion of the ambo- 

 ceptor in Lillie's fertilizin hypothesis into 

 which sperm receptors fit in the fertiliza- 

 tion reaction. 



SPERM RECEPTOR - chemical group associ- 

 ated with the spermatozoa, reacting with 

 fertilizin (amboceptor) in Lillie's side chain 

 hypothesis of the fertilizin reaction. 



SPINA BIFIDA - split tail caused by a variety of 

 abnormal environmental conditions such as 

 heat, cold, lack of oxygen, centrifugation, 

 any of which may prevent the proper closure 

 of the blastopore which leads to this split- 

 tailed condition. 



STEPWISE INHIBITION - successive inhibitions 

 of organic processes by successively 

 stronger applications of external agents. 



STEREOBLASTULA - solid blastula experiment- 

 ally produced by subjecting (Echinoderm) 

 eggs to alkaloids; normal blastocoel filled 

 with solid mass of cells (e. g. , Crepidula). 



STERILITY, SELF - inability of eggs and sperm 

 of the same (hermaphroditic) individual to 

 fuse and give rise to an embryo (e. g. , Ciona 

 intestinalis, an Ascidian). 



STERNOPAGUS - sternal union of conjoined twins. 



STICOTROPISM - faculty of acquiring and losing 

 claviform shape of the bottle cells of the 

 blastoporal lip during gastrulation (Ruffini, 

 1925). 



STIMULATION, DIFFERENTIAL - varying res- 

 ponses of a gradient system to favorable con- 

 ditions, as when an optinnally high tempera- 

 ture is applied to a regenerating Planarian 

 and a bigger and better head results than 

 under normal (temperature) conditions. 

 (See inhibition, differential. ) 



STIMULUS, FORMATIVE - concentration of 



(chemical) substance in the dorsal lip of the 

 blastopore leading to the formation and de- 

 marcation of embryonic fields. 



STIMULUS, OXYGENOTACTIC - differential 



stimulation of a developing organism by ex- 

 posure to oxygen. Presumably a factor in 

 the spreading of the blastoderm (chick) over 

 the yolk. Syn. , oxygenotaxis. 



STORE'S LAW - formula for determining vis- 



2cE (rf - p)a2 



cosity V = 2-^- ^ — 



9 qn 



(formula generally omits c and q) where V 



is the speed at which granules travel through 



cytoplasm under a centrifugal force of cq 



absolute units; g is the gravity constant; 



