OF EXPERIMENTAL WORK I5I 



Trypsin, in Dendraster excentricus (A. R. Moore, 1951a). 



Hypertonic sea water, in Ps. microtuberculatus (E. B. Harvey, 1938a). 



Clear Quarter-Eggs. — Fertilized, become amoeboid if not cleaved (E. B. Haryey, 

 1946). Clear quarter-eggs and white half-eggs, made parthenogenetic with ultra- 

 violet light, become amoeboid (E. B. Harvey and Hollaender, 1938). 



Arrest of Amoeboid Movement. — By high hydrostatic pressure on urea-treated eggs. 

 By lack of oxygen (Kitching and Moser, 1940). 



Other Species (additional) 



Dendraster excentricus WiXh. trypsin (A. R. Moore, 1951a). 



Paracentrotus lividus and Ps. microtuberculatus, upper half (with nucleus) of centrifuged egg 



(E. B. Harvey, 1934, p. 239). 

 Sphaerechinus granularis, whole centrifuged egg and lower (non-nucleate) half of centrifuged 



egg (E. B. Harvey, 1938a, p. 184). 



ANAEROBIOSIS 



See Oxygen-Lack 



ANAESTHETICS (nARCOTICS) 



Effect on Size of Egg. — Volume increase in 3 % ether (Heilbrunn, 1928, p. 203); in 

 chloroform (Heilbrunn, 1915a). 



Effect on Shape of Egg. — Eggs become amoeboid if kept in 0.2 M ethyl urethane for 

 one hour (E. B. H. per E. N. Harvey, 1933). Elongate, centrifuged eggs also become 

 amoeboid. These can be fertilized, the fertilization membrane following the irregular 

 contour; they cleave in the irregular shape on return to sea water. If not fertilized 

 the amoeboid eggs become spherical on return to sea water (E. B. H., 1931 unpub.). 



Fertilization. — Eggs can be fertilized in alcohols, but do not cleave; cannot be 

 fertilized in ethyl acetate though sperm surround the eggs (Blumenthal, 1928). Can 

 be fertilized in o. 1 5 M ethyl urethane, sometimes forming a fertilization membrane 

 (E.B.H.). 



Surface Precipitation Reaction. — May be prevented by anaesthetics (Heilbrunn, 



1934)- 



Cleavage. — Effective concentrations of many anaesthetics for reversible arrest of 

 cleavage are given in Table 13, from R. S. Lillie (1914b). Effective concentrations 

 of some urethanes for reversible arrest of cleavage are given in Table 14 (E. B. H. 

 per E. N. Harvey, 1932 a). 



Mitotic Figure.— AndiC%x.\\tX.\c% (many) may prevent formation of spindle and cause 

 rays to disappear (Heilbrunn, 1920a, b). Urethanes cause astral eays to fade out 

 and cleavage planes to disappear (Painter, 19 18; E. B. H., 1930 unpub.). When 

 placed in 0.2 M ethyl urethane at metaphase, cleavage planes fade out and when 

 returned to sea water are replaced irregularly, but normal blastulae may be formed 

 (E. B. H.). These phenomena are similar to those described and figured by me 

 (1927, 1930) for eggs kept without oxygen. A similar disappearance of cleavage 

 planes also is caused by high hydrostatic pressures (Marsland, 1938, 1939, 1950, 

 1 951) and in Ps. microtuberculatus by mechanical pressure (Boveri, 1897). Disappear- 

 ance of astral rays by various agents was first found by O. and R. Hertwig in 1887 

 in Paracentrotus lividus, and very carefully studied by E. B. Wilson (1901 b) in ether- 

 ized eggs of Toxopneustes (Lytechinus) variegatus ; he also studied obliteration of 

 cleavage furrows. 



Monasters formed with chloral hydrate were described in P. lividus by O. and R. 

 Hertwig (1887); in Lytechinus in etherised eggs (E. B. Wilson, 1901b); in P. lividus 

 and A. punctulata with phenyl urethane (Painter, 1915, 1916, 1918). 



