OF EXPERIMENTAL WORK 211 



and usually perpendicular to stratification. Delays cleavage (E. B. H., 1933 unpub. ; 

 Marsland, 1938; Kitching and Moser, 1940). 



Temperature and pressure. — Lowered temperature acts like increased pressure (Mars- 

 land, 1950); see Brown (1934). 



Adenosine triphosphate. — Counteracts inhibiting effects of pressure (Marsland, 

 Landau, and Zimmerman, 1953). 



Insemination. — Prevented at 6,000 lbs/in^, but sperm are active (Marsland, 1948). 



Amoebocytes. — Become spherical at 400 atmospheres (Marsland, 1938). 



Moderately High Pressures. — (61 atmospheres) of nitrogen and helium have no effect 

 on cleavage; nitrous oxide delays cleavage at 2.3 atmospheres (Haywood, 1953). 



B. Internal Pressure. 



Internal Pressure. — Of unfertilized egg is 40 dynes per cm.^ (Cole, 1932). Internal 

 pressure of unfertilized egg necessary to rupture the membrane, is of order of i/ioo 

 atmosphere. Effect of hypotonic sea v/ater, salts, pH, anaesthetics, ultraviolet light, 

 trypsin on resistance to internal pressure (Rieser, 1950). 



Internal pressure. — Of fertilized egg, calculated from Chambers' experiment of 

 rupturing one of two blastomeres, 62 dynes per cm.^ (Sichel and Burton, 1936; 

 see Chambers, 1938 c). 



C. Mechanical Pressure. 



Method. — Cover slip or compressorium. 



Position of Cleavage Planes and Micromeres. — Changed, cells forming flat plates 

 (Morgan, 1893). 



Obliteration of Cleavage Plane. — In Psammechinus microtuberculatus (?) (Boveri, 1897). 



Other Species (additional) and General References 



Driesch, 1892. Echinus (Psammechinus) microtuberculatus, mechanical pressure. 



Lepeschkin, 1941a. A. lixula etc., mechanical pressure. 



Marsland, 1939, 1951- A. lixula, hydrostatic pressure. 



Marsland, 1942. General. 



Marsland and Landau, 1950. Echinarachnius parma, hydrostatic pressure. 



Morgan, 1927, p. 468. Experimental Embryology. Mechanical pressure, general. 



Pease, 1942 a. Strongylocentrotus purpuratus, hydrostatic pressure. 



Ziegler, 1894. Echinus (Psammechinus) microtuberculatus, mechanical pressure. 



PROTEINS 



See also Nucleoproteins 



Protein is assumed to be 6.25 times the nitrogen present, by weight. 



Amount in Egg. — About 65 % of egg dry weight is protein (Hutchens, Keltch, Krahl, 

 and Clowes, 1942). 



Change on Fertilization. — 12 % of total protein becomes insoluble 3 to 10 minutes 

 after fertilization (Mirsky, 1936; known as "Mirsky protein"). See Monroy and 

 Oddo (1951) for A. purutulata and A. lixula. 



Amount in Seminal fluid. — About 2.5 mg. per cc. undiluted seminal fluid (Hayaslii, 

 1945, 1946). 



On Sperm Surface. — (Hayashi, 1945, 1946; Popa, 1927, lipoprotein). 



Basic Proteins. — (Protamines and histones) extracted from sperm, cause agglutin- 

 ation (Metz, 1949); see Frank (1939). 



Other Species and General References 



Conners and Scheer, 1947. 5. purpuratus, analysis of protein. 



Ephrussi, 1933. P. lividus, protein is 66.88% of dry weight. 



Hultin, 1949a. A. lixula, P. lividus, Ps. miliaris, Echinocardium cordatum, basic proteins. 



