OF EXPERIMENTAL WORK I 85 



Strongylocentrotus drobachiensis X S. pallidas (Vasseur, 1952 b). 



Strong ylocentrotus purpuratus X S. drobachiensis (Swan, 1953 Evolution 7 : 269). 



Strongylocentrotus pur puratus X S . franciscanus (Swan, 1953). 

 Methods of Increasing Hybridization. — 



Heavy insemination (F. R. Lillie, 1921c). 



Standing in sea water (Tennent, 1910b, 1923). 



Egg water (Hultin, 1948 b; Harding and Harding, 1952 a). 



Hyperalkalinity (Tennent, 1910b, 1923; Loeb, 1913 a, p. 225, 1915a). 



Heat (Herbst, 1906). 



Remove jelly (Harding and Harding, 1952 b). 



Remove vitelline membrane with trypsin or urea, adding glycine, bovine albu- 

 men, etc. (Hultin, 1948a, b; Bohus-Jensen, 1953) ; does not work with A. punc- 

 tulata (Tyler and Metz, 1954). 



Crowd the eggs (E. B. Harvey, 1941 d). 



Cleavage Rate of Hybrid. — Is that of the egg (Tennent, 1910b, 1922; A. R. Moore, 

 1933 in Dendraster X S . franciscanus ; De Francesco, 1934, in Naples species). 



Variability of Hybrids. — (Shearer, De Morgan, and Fuchs, 1914; Horstadius, 1940). 

 Tennent (19 13, p. 536) writes "It has been established again and again that under 

 some conditions we may obtain larvae of a maternal type with respect to certain 

 characters, under other conditions larvae of a paternal type and under still other 

 conditions larvae of a blended type. This is established. We should accept the fact." 



Other Species and General References (Inconnplete) 

 Bohus-Jensen, 1953. Bermuda species. 



Bronn's Tierreich, 1904, Bd. 2, Abt. 3, Buch IV : 1238-1251 . 

 De Francesco, 1933. Naples species. 

 Fuchs, 1914b, F2 Echinus hybrids. 

 Harding and Harding, 1952a, b. A. lixula X P. lividus and Echinocardium cordatum X Psam- 



mechinus miliaris. 

 Harvey, E. B., 1933 a. Naples species. 

 Harvey, E. B., 1942. Echinarachnius parma X S. drobachiensis, maternal; S. franciscanus X 'S'. 



purpuratus, maternal, but see A. R. Moore, 1943. 

 Harvey, E. B., i^i^i . Lytechinus variegatus X Tripneustes esculentus, ma.terna.1. 

 Herbst, 1906-19 14. ... 



Horstadius, 1936c. Psammechinus mjcrotuberculattu < Paracentrolus lividuj/' 

 Hultin, 1948a, b. Naples species. 

 Matsui, 1924. List of hybrids. 



Moore, A. R., 1949c. Portugaliae Acta Biologica, Ser. A. 

 Morgan, 1927. Experimental Embryology. General. 

 Niimann, 1933. Naples species. 

 Runnstrom, 1949a, 1952a. General. 



Shearer, De Morgan, and Fuchs, 191 4. Psammechinus miliaris, Echinus esculenlus and E. aculus. 

 Tabulae Biologicae, 1930, VI : 514. Grimpe. 

 Tennent, 1910 b. List of hybrids. 



Tennent, 1912 a. Lytechinus variegatus X Tripneustes esculenlus. 

 Tennent, 1922. Cidaris tribuloides. 

 Tennent, 1923. Japanese species. 



von Ubisch, 1937. Echinocyamus pusillus X Ps. miliaris. 

 von Ubisch, 1 939. Echinocardium cordatum X Ps. miliaris. 

 Wilson, 1925. The Cell. 



HYDROGEN ION CONCENTRATION, PH 



Sea Wat:r at Woods Hole. — pH usually taken as approximately 8.0 (Heilbrunn, 1943, 

 p. 473). Other values are 8.1 to 8.3 (Redfield, 1948, etc.). See Ball and Stock (1937). 

 pH in relation to COo content (Henderson and Cohn, 19 16; McClendon, 19 16). 



