OF EXPERIMENTAL WORK 167 



Reducing Sugar. — Absent (Perlzweig and Barron, 1928; Hutchens, Keltch, et al., 



1942)- 



Cholesterol. — Present (Mathews, 19 13). 



Lactic Acid. — 3.14 mg. per gm. egg protein. 19 % increase in 4-8 cell fertilized eggs 

 (Perlzweig and Barron, 1928), not confirmed by Hutchens, Keltch, et al. (1942). 



Echinochrome. — See Echinochrome. 



Enzymes. — See Enzymes and Cytochrome. 



Other Species and General References 



Bialaszewicz, 1927, 1929. A. lixula and Paracentrotus lividus, electrolyte content. 

 Ephrussi and Rapkine, 1928, and Ephrussi, 1933. Paracentrotus lividus, protein, fat, carbo- 

 hydrate, ash. 

 Harvey, E. N., 1932 a. Constants, general. 

 Krahl, 1950. General. 



Leitch, 1934b, 1936. S.franciscanus, S. purpuratus, nitrogen, lipoid, ash. 

 Lindberg, 1943. Echinocardium cordatum, phosphate fractions. 



Malm and Wachtmeister, 1950. Psammechinus miliaris, S. drobachiensis, potassium content. 

 Mitchinson and Swann, 1953. Ps. miliaris, 25.5% solids. 

 Needham, 1931 and 1942. General. 



Orstrom and Lindberg, 1940. Paracentrotus lividus, carbohydrate content and metabolism. 

 Pantin, 1931. Body fluids, composition. 



Rothschild and Barnes, 1953. Electrolyte content of many species. 

 Stott, 1 93 1. Echinus esculentus, carbohydrates. 



Tennent, Gardiner, and Smith, 1931. Echinomeira lucunter, lipids and glycogen. 

 Wetzel, 1907. Paracentrotus lividus, per cent of solid, fat, Nj, P, ash. 

 Zielinsky, 1939. Paracentrotus lividus, phosphate fractions and carbohydrate metabolism. 



CORTICAL LAYER 



Position. — A layer just beneath the plasma membrane and above the mass of cyto- 

 plasm (Figs 9, 10). According to Parpart and Laris (1954) it is outside the plasma 

 membrane. 



Properties. — A relatively rigid gel, comparatively clear ; may be liquified reversibly 

 (Danielli, 1942, p. 86). Its thickness is 0.8 [i. in A. punctulata; i [i. to 2 [z in some forms 

 (Runnstrom and Monne, 1945a; Mitchison, 1952). Cortex of centrifuged unfertil- 

 ized egg is bright in dark field (Moser, 1939a) and is birefringent (McCulloch, 

 1952 a). Cortical layer contains calcium proteinate (Heilbrunn, 1952, p. 465, 538). 

 Bound calcium in cortex of fertilized eggs can be released by potassium (Churney 

 and Moser, 1940). 



Liquefaction. — By Micromanipulation (Chambers, 1935b, 1938b). Hydrostatic 

 pressure (Brown, 1934; Mailand, 1938, 1950, 1951). Decreased temperature (Mars- 

 land, 1950). 



Stiffens. — With calcium (Heilbrunn, 1952, p. 97). 



Cortical Granules. — In cortical layer, they disappear 20 seconds after fertilization or 

 parthenogenesis and help form the fertilization membrane. The granules are approxi- 

 mately 0.8 pL in diameter and are not displaced by high centrifugal forces, 6,000 x 

 g (Moser, 1939a, b, 1940); 10,000 x g (E. B. Harvey, 1946a). The cortical reac- 

 tion takes about 10 seconds at 25.7° C. (Moser, 1939a). These granules were first 

 observed and described in Arbacia by E. N. Harvey (191 1, p. 523) as minute granules 

 unmoved by the centrifuge, which disappear on fertilization and whose substance 

 helps to form the fertilization membrane. These granules were observed and figured 

 in the unfertilized egg of Echinus esculentus, and their absence in the fertilized egg 

 was noted by Gray (1924, p. 169; by an error they are called "micromercs" instead 



