GLOSSARY U69 



INVOLUTION - rotation of a sheet of cella upon Itself; movement directed toward the Interior of an egg; the 

 rolling Inward or turning in of cells over a rim. One of the movements of gastrulatlon (e.g., chiok) . 

 Syn., embolic Invagination (Jordan); einrollung, or umachlag (Vogt). 



lEIDlOCYTES - inorganic salt crystals. 



ISAUXESIS - relative growth comparisons in which the rate of the part Is the same as that of the whole. 

 (Syn., isogony.) (Needham, igltO.) 



ISO- AGGLUTININ - (Syn., for fertilizln.) 



ISO-ELECTRIC POINT - set of conditions under which the protein tends to give off hydrogen ions Just suffi- 

 cient to balance the tendency to give off hydroxyl ions; a state where the Ionization of the protein 

 Is balanced. 



ISOGONY - proportionate growth of parts so that growth coefficient is unity and there are constant relative 

 size differences. Equivalent relative growth rate. 



ISOLATION - removal of a part of a developing organism and Its maintenance In the living condition as in 

 tissue cultures. Physiological Isolation may be achieved by Interposing a mass of Inert material 

 (e.g., yolk) between two regions. The bifurcations of regenerating limbs or the production of double 

 hearts by interposing an Inert barrier or one which is not subject to assimilative induction. 



ISCMBTEY - study of relative sizes of parts of animals of the same age. 



ISOTROPIC - synonym for pluripotent (Lillie, I929). 



ISOTROPy - originally used (Pfluger, 1883) to mean absence of predetermined axes within the egg; now means 

 condition of egg where any part can give rise to any part of the embryo (i.e., equivalence of all 

 parte of the egg protoplasm) . 



JANICEPS - Janus monster, face to face union of conjoined twins. 



JANUS EMBRYO - double monster with faces turned in opposite directions. Syn., duplicitas cruclata typlca. 

 JELLY - mucin covering of (amphibian) egg, derived from the oviduct and applied to the outside of the 

 vitelline membrane. In Frog, apparently necessary for successful fertilization. 



KEEN-PLASMA RELATION - ratio of the amount of nuclear and of cytoplasmic materials present In the cell. 



It seems to be a function of cleavage to restore the kem-plaema relation from the unbalanced condi- 

 tion of the ovum (with its excessive yolk and cytoplasm) to the gastrular or the somatic cell. 



KINETOCHORE - spindle fiber attachment region. Syn., centromere. 



LAEOTROPIC - turned, colled, inclined to the left or counter-clockwise. Syn., lelotroplc. 



LAMP-BRUSH EFFECT - the side branches and loops from the chromosomes of young oScytea give such an ap- 

 pearance. Syn., "Bursten" effect of Ruckert and Camoy. 



LARVA - stage in development when the organism has emerged from its membranes and Is able to lead em 

 independent existence, but may not have completed its development. Except for neotony and paedo- 

 genesis, larvae cannot reproduce themselves. 



LARVAL CHARACTERS - characters seen In the larva which may be dominant or recessive (as indicated when 

 hybrid crosses are reversed) but which are not dependent upon an Fg to determine the status. E^ 

 cytoplasm Is dominant over sperm influences In early development of hybrids. Larval skeletal dif- 

 ferences seen In Echlnoderm larvae of different combinations. 



LATERAL LINE SYSTEM - a line of sensory structures along the side of the body of fishes and larval 



amphibia, generally embedded in the skin and Innervated by a branch from the vagus ganglion. Pre- 

 sumably concerned with the recognition of low vibrations in the water. 



LEAST SURFACE PRINCIPLE OF PLATEAU - homogenous system of fluid lamellae so arrange themselves that the 

 individual lamellae adopt a curvature such that the sum of the (external) forces of all Is, under 

 the specific conditions, at a minimum. 



LECITHIN - organismlc fat which Is phosphorlzed in the form of phosphatides. 



LETHAL DEFECT - the suppression of a vital organ or of some vital function by a local defect. 



LIESEGANG'S FIGURES - process of stratification as of formative substances in the egg. 



LIMICOLA CELL TYPE - the movement of Isolated embryonic cells resembles that of Amoeba limlcola 

 (Rhumoler, I898) having balloon-like pseudopodla. 



LIPIN - fats and fatty substances such as oil and yolk (e.g., lecithin) in eggs. Important as water 

 holding device in cells as well as Insuring cell immisciblllty with surrounding media. (E.g., 

 cholesterol, ergosterol.) 



LIPOGENESIS - omission of certain stages in ontogeny. 



LIPOPHORES - pigmented cells In the dermis and epidermis, derived from neural crests and characterised 

 by having diffuse yellow (llpochrome) pigment in solution. 



LIPOSOMES - droplets of yellow oil which may be formed by the coalescence of droplets of broken down 

 lipochondria (Holtfreter, I9U6). 



LITHOPEDION - mummified or calcified fetuses; "stone-child". 



LOBSTER CLAW - missing digits in hands or feet, or split hand or foot; probably inherited. 



LOCALIZATION - cytologlcal separation of parts of the mosaic egg, each of which has a known specific 

 subsequent differentiation. There is often a substratum associated with these areas, made up of 

 pigmented granules, but It Is the cytoplasm rather than the pigmented elements in which localiza- 

 tion occurs. 



