OF EXPERIMENTAL WORK 183 



in the cleavage furrow (McClendon, 1910b; Painter, 1918; Just, 1928 b; E. B. 

 Harvey, 1934; Chambers, 1938c). It is increased in thickness by hypertonic sea 

 water (E. B. Harvey, 1940a, Photograph i, p. 205; Gray, 1924, 1931, p. 198, in 

 E. esculentus). 



Structure. — Gelatinous film (Loeb, 1913a, p. 19); tough, sticky, fibrous, elastic; 

 can be torn with micro-needles (Chambers, 1921a, 1930, 1940). Is probably a 

 calcium proteinate (A. R. Moore, 1928 a, 1949 b in S. purpuratus) ; see Chapter 6 of 

 Gray's Experimental Cytology (1931). 



Stains. — With isamine blue, toluidin blue (Kite, 191 2). It does not stain with 

 methylene blue, brilliant cresyl blue or neutral red (E. B. Harvey, 1934). 



Function. — Binds blastomeres together (Herbst, 1900 in Ps. microtuberculatus) . For 

 Arbacia punctulata see McClendon, 1910b; Chambers, 1921a, 1930, 1938c, 1940; 

 E. B. Harvey, 1946a; et al. Important in cell division (Just, 1928 a; Gray, 1924, 

 1 93 1, p. 196 in E. esculentus). See Plate XVI, Photograph 9. 



Ca-free sea water. — Dissolves. See Calcium for preparation. For Arbacia see (E. B. 

 Harvey, 1934; Chambers, 1940; et al.). 



Isosmotic KCl. — Dispersed by (Chambers, 1940, 1944; Kopac, 1940a, 1941a). By 

 lithium (Chambers, 1940). 



NaCl + KCl. — 0.52 M in proportions 19 : i at pH 7; is non-toxic (Chambers, 

 1938 c, 1940; Kopac, 1940 a). 



Papain, Trypsin and Ficin. — Dissolved by enzyme papain, not by trypsin or ficin 

 (Northrop, 1947; E. B. H.). Bohus-Jensen (1950) also found it not dissolved by 

 trypsin or ficin (in Ps. miliaris, etc.). There is disagreement about trypsin; Runn- 

 strom, Monn^, and Broman (1944) found that trypsin did dissolve the hyaline layer 

 in Ps. miliaris ; and A. R. Moore (1951 a) in Dendraster excentricus, but not (1949 a, b) 

 in S. purpuratus. There may be differences in the trypsin used or in the reaction of 

 different species, or differences due to the time when the trypsin is used. 



Aceto-carmine . — Dispersed by aceto-carmine, forming spheres, which unite and 

 form striations in perivitelline space (E. B. Harvey, 1950, unpub.). 



Urea. — Prevents formation (A. R. Moore, 1930a, 1949a, in S . purpuratus) . 



Twins.— \^\icn dissolved, in 2-cell stage twins are formed (E. B. Harvey, 1940 a; 

 1935b in Ps. microtuberculatus ; Loeb, 1909b in S. purpuratus) . Plate XVI, Photo. 8. 



Hatching Enzyme. — Not dissolved by (Kopac, 1941a). 



X-ray Effect. — (Kopac, 1941b). 



Replaced. — After removal (E. B. Harvey, 1934, 1935b; Kopac, 1940a; Gray, 1931, 

 p. 212, in E. esculentus). 



Centrifugal force . — Hyaline layer is thrown off as a crescent in Arbacia, as a ring in 

 Ps. microtuberculatus, lying in the perivitelline space at the centrifugal pole. (Plate 

 XVI, Photograph 6). This can be dissolved in calcium-free sea water, and re-precipi- 

 tated in sea water (E. B. Harvey, 1934). 



Coalescence. — With oil drops, none (Kopac, 1940a, 1941a; Chambers, 1944). 



Permeability. — Freely permeable to electrolytes (Chambers, 1940; Gray, 1931, 

 p. 1 98 in Echinus esculentus) . 



Other Species (additional) and General References 



Dan and Ono, 1952. Mespilia globulus. 



Dan, Yanagita, and Sugiyama, 1937. Mespilia globulus. 



Goldschmidt and Popoff, 1908. P. lividus, Ps. microtuberculatus. 



Gray, 1924. Echinus esculentus. 



Gray, 1931. Experimental Cytology, general; chapt. 6 and 9. 



Just, 1939b. The Biology of the Cell Surface. General. 



Moore, A. R., 1949a, b; 1951b. Review. 



Morgan, 1927. Experimental Embryology, p. 138. General. 



