GLOSS7\ilY 



485 



KERN-PLASMA RELATION - ratio of the 



amount of nuclear and of cytoplasmic ma- 

 terials present in the cell. It seems to be 

 a function of cleavage to restore the kern- 

 plasma relation from the unbalanced con- 

 dition of the ovum (with its excessive yolk 

 and cytoplasm) to the gastrular or the 

 somatic cell. 



KINETOCHORE - spindle fiber attachment re- 

 gion. Syn. , centromere. 



LAEOTROPIC - turned, coiled, inclined to the 



left or counter-clockwise. Syn. , leiotropic. 



LAMP-BRUSH EFFECT - the side branches and 

 loops from the chromosomes of young 

 oocytes give such an appearance. Syn. , 

 "Biirsten" effect of Ruckert and Carney. 



LARVA - stage in development when the organ- 

 ism has emerged from its membranes and 

 is able to lead an independent existence, 

 but may not have completed its development. 

 Except for neotony and paedogenesis, lar- 

 vae cannot reproduce themselves. 



LARVAL CHARACTERS - characters seen in 

 the larva which may be dominant or reces- 

 sive (as indicated when hybrid crosses are 

 reversed) but which are not dependent upon 

 an Ft to determine the status. Egg cyto- 

 plasm is dominant over sperm influences 

 in early development of hybrids. Larval 

 skeletal differences seen in Echinoderm 

 larvae of different combinations. 



LATERAL LINE SYSTEM - a line of sensory 

 structures along the side of the body of 

 fishes and larval amphibia, generally em- 

 bedded in the skin and innervated by a 

 branch from the vagus ganglion. Presum- 

 ably concerned with the recognition of low 

 vibrations in the water. 



LEAST SURFACE PRINCIPLE OF FLATEAU - 

 homogenous system of fluid lamellae so 

 arrange themselves that the individual la- 

 mellae adopt a curvature such that the sum 

 of the (external) forces of all is, under the 

 specific conditions, at a minimum. 



LECITHIN - organismic fat which is phosphor - 

 ized 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 stratifica- 

 tion as of formative substances in the egg. 



LIMICOLA CELL TYPE - the movement of 



isolated embryonic cells resembles that of 

 Amoeba limicola (Rhumbler, 1898) having 

 balloon-like pseudopodia. 



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 in- 

 suring cell immiscibility 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 characterized by having diffuse yellow 

 (lipochrome) pigment in solution. 



LIPOSOMES - droplets of yellow oil which may 

 be formed by the coalescence of droplets of 

 broken down lipochondria (Holtfreter, 1946). 



LITHOPEDION - mummified or calcified fetuses; 

 "stone-child". 



LOBSTER CLAW - missing digits in hands or 

 feet, or split hand or foot; probably inher- 

 ited. 



LOCALIZATION - cytological 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 gran- 

 ules, but it is the cytoplasm rather than the 

 pigmented elements in which localization 

 occurs. 



LUNAR PERIODICITY - maturation and ovipo- 

 sition during certain phases of the lunar 

 cycle (e. g. , Nereis limbata sheds its gam- 

 etes in the period from the full moon to the 

 new moon in June to September). 



MACERATION - to swell by soaking. In water 

 the connective tissue between cells is 

 loosened and the cells tend to separate. 



MACROCEPHALUS - abnormally large head due 

 to abnormal development of the cranium. 

 Often the brain is swollen with cerebro- 

 spinal fluid. Syn. , hydrocephalus. 



MACROMERE - larger of the blastomeres where 

 there is a conspicuous size difference, gen- 

 erally the yolk-laden endoderm forming 

 cells. Opposed to micromere. 



MACROSOMIA - gigantism, enlarged skeleton 



due to disturbed function of the pituitary and 

 possibly also the thyroid glands. 



MACROSTOMUS - failure of the primitive mouth 

 slit to reduce normally. 



MARGINAL BELT - ring of presumptive meso- 

 derm of the amphibian blastula, essentially 

 similar to the grey crescent of the undivided 



egg- 



MATRIX - ground substance surrounding the 



chromonemata, usually less chromatic and 

 making up the body of the chromosome. 

 Syn. , kalymma or hyalonema. 



MATRIX, INTERCELLULAR - the cytoplasmic 

 wall substance of cells in a whole blastema 

 which forms an integrated foam structure 

 and, because of its continuity, shows a very 

 definite syncitial character. (Moore) 



MATURATION - the process of transforming a 

 primordial germ cell (spermatogonium or 

 oogonium) into a functionally mature germ 

 cell, the process involving two special divi- 

 sions, one of which is always meiotic or re- 

 ductional. 



