GLOSSARY 



479 



take place (e. g. , heart or limb fields). 

 Dynamic system of interrelated parts in 

 perfect equilibrium in the undifferentiated 

 organism. Not a definite circumscribed 

 area (like a stone in a mosaic) but a center 

 of differentiation with intensity diminishing 

 with the distance from the center, and with 

 different fields overlapping (Harrison, 1918). 

 A system of patterned conditions in a self- 

 sustaining configuration (Weiss, 1926). 

 Has a material substratum which may be 

 reduced without fundamentally altering the 

 original field pattern. Field is both hetero- 

 axial and heteropolar. "Morphe concept" 

 of Gurwitsch (1914). 



FIELD, DISTRICT - a district whose activities 

 show field character although none of its 

 elements can be identified with any particu- 

 lar component of the field. 



FIELD, GRADIENT - the direction along which 



the field intensity changes most rapidly. 

 •FIELD, HETEROAXIAL - field in which develop- 

 ing structures vary along three coordinates 

 in space. 



FIELD, HETEROPOLAR - the effects within a 

 field differ in two opposing senses along 

 the same axis. 



FIELD, INDIVIDUATION - fields are under the 

 control of the organizing forces of the host 

 whose differentiation leads toward the real- 

 ization of a complete individual. 



FIELD LAWS - (1) When material is split off 



from a field bearing system, 

 that portion remaining con- 

 tains the field in its typical 

 distribution and structure. 



(2) When unorganized but labile 

 material enters the field it 

 is included within the field. 

 Any field spreads over the 

 whole of the material at its 

 disposal, preserving its 

 initial structure even though 

 somewhat enlarged. 



(3) Fields have the tendency of 

 taking up and including within 

 themselves any equivalent 

 fields from contiguous en- 

 vironment (e. g. , whole em- 

 bryos formed from two fused 

 eggs). (See Schotte, 1940: 

 Growth suppl. p. 64. ) 



FIELD, MORPHOGENETIC - embryonic area out 

 of which specific structures will develop; 

 fields which determine the development of 

 form in a unitary structure (Gurwitsch, 

 1930). 



FIELD, ORGAN - area in which a specific organ 

 of the embryo will develop (e. g. , eye field). 



FIELD, TACTIC - field governing the displace- 

 ment of cells (e. g. , grouping of cells in the 

 cartilaginous primordium of the amphibian 

 skeleton - Anikin, 1929). 



FIELD, VEGETATIVE - early differentiated 



part of the Echinoderm embryo; presump- 

 tive endoderm. 



FOLLICLE - a cellular sac within which the egg 

 generally goes through the maturation stages 

 from oogonium to ovum; made up of follicle 

 cells, theca interna and externa. 



FOVEA GERMINATIVA - pigment-free spot of 

 the animal hemisphere where the amphibian 

 germinal vesicle gives off its polar bodies. 



FRAMBOISIA - protrusion of cells following 

 treatment of the embryo with anisotonic 

 solutions (Roux). 



FREEMARTIN - mammalian intersex due to 



masculinzation of a female by its male part- 

 ner when the foetal circulations are contin- 

 uous and the sex hormones are intermingled, 

 as in parabiosis. 



FUNCTION, HOMOLOGOUS - synchronous be- 

 haviour (e. g. , when supernumerary limbs 

 are grafted near the control limb, they may 

 acquire innervation from the plexus of the 

 control and will thereafter contract syn- 

 chronously and with the same degree of in- 

 tensity as the control) (Weiss, 1936: Biol. 

 Rev. 2 -Resonance Theory of Reflex Activity.) 



FURCHUNG - division of the egg cell into blas- 

 tomeres by mitosis. 



GALVANO-NEUROTROPISM - differences in 

 electrical potential responsible for growth 

 and connections of developing nerves. Gal- 

 vanic forces in neurogenesis. 



GAMETE - a differentiated (mature) germ cell, 

 capable of functioning in fertilization, (e. g. , 

 spermatozoon, ovum.) Syn. , germ cell. 



GAMETOGENESIS - the process of developing 

 and maturing germ cells. 



GASTROSCHISIS - improper closure of the body 

 wall along the mid-ventral line. 



GASTRULA - the didermic or double-layered 

 embryo, possessing a newly formed cavity 

 known as the gastrocoel or archenteron. 

 The two layers are ectoderm (external) and 

 endoderm (internal) with only positional 

 significance when first formed. 



GASTRULATION - dynamic processes involving 

 cell movements which change the embryo 

 from a monodermic to a di- or tri-dermic 

 form, generally involving inward movement 

 of cells to form the enteric endoderm. 

 Process varies in detail in different forms, 

 but may include epiboly, concrescence, con- 

 fluence, involution, invagination, extension, 

 convergence - all of which are descriptive 



terms for morphoeenetic movements. 

 " i o ... 



GEFALLE - a continuous, quantitative grada- 

 tion of a definite condition within a cell 

 colony. (See gradient) 



GEL - a system in which there is a reduction in 

 the amount of solvent relative to the amount 

 of solid substance, thereby causing the 

 whole to become viscous (e. g. , asters). 



