OF EXPERIMENTAL WORK I9I 



MAGNESIUM 



Amount in Egg. — 4.48 mg. magnesium per 10* eggs (10' eggs = o. 124 gm. dry weight), 

 or 0.182 millimoles (Page, 1927 b). 



Amount in Sea Water. — At Woods Hole 1.3004 gm. per liter at 20^ C. (Page, 

 1927c, 1928). 



MgCl^ Isotonic. — With sea water at Woods Hole is 0.30 M (M. B. L. Chemical 

 Room). Also given as 0.37 M. MgS04 isotonic with sea water at Woods Hole 

 may be 0.81 M (M. B. L. Chemical Room). Also given as 0.52 M. 



Surface Precipitation Reaction. — Mg acts like Ca but is less potent (Heilbrunn, 1930, 



I934> 1943. P- 470, 538). 



Cytolysis. — Prevented by MgClg (R. S. Lillie, 1911a, b; Page, 1924). 



Mg Counteracts NaCl. — And other Na and K salts (Loeb, 1900 a; Mathews, 1905; 

 R. S. Lillie, 1911a, b, 1914a; McCutcheon and Lucke, 1928). Mg is antagonized 

 by Ca (Heilbrunn, 1934; HoUingsworth, 1941). 



Colorless Amoebocytes of Body Fluid. — Dissolved by MgCIj (Mathews, 1900). 



Amoeboid Eggs. — Caused by MgClj (Loeb, 1900a; Churney, 1940). 



Effect of Mg on Fertilized Eggs. — Nuclear division without cell division (Loeb, 

 1895b, 1900a; Norman, 1896). Astropheres present also (Morgan, 1899). 



Mg as an Anaesthetic. — MgS04 widely used to quiet marine organisms (Mayor, 

 1909; R. S. Lillie, 1910, 1916c; Heilbrunn, 1934, 1943, p. 460; 1952, p. 528). First 

 used by TuUberg in 1892 (see last reference of Heilbrunn). Mg anaesthesia counter- 

 acted by Ca (Heilbrunn, 1943, p. 531). Magnesium sulfate can be used on blastulae 

 and plutei of Arbacia. "Methocoel", methyl cellulose, also quiets cilia (Marsland, 

 1943); also Chloretone. See McClung's Microscopical Technique, 1950, p. 436. 



Respiration. — No references found. 



Permeability. — Decrease (R. S. Lillie, 19 10; McCutcheon and Luck^, 1928; Heil- 

 brunn, 1943, p. 531)- 



Viscosity. — (Better stratification with decreased viscosity). MgClj decreases visco- 

 sity (Heilbrunn, 1923, 1928, p. 147, 1943, p. 81; E. B. Harvey, 1945). Isosmotic 

 solutions arranged in order of their effect in decreasing viscosity (better stratification) : 

 CaClg > MgCla > sea water > NaCl > KCl (E.B.Harvey, 1945). Heilbrunn 

 1928, p. 147) gives them in the same order except that K and Na are reversed. 



Breaking with Centrifugal Force. — Break less readily in MgClj than in sea water. 

 Isosmotic solutions arranged in order of their effectiveness in causing breaking into 

 halves, proceed in the reverse order from that given above for decrease in viscosity ; 

 the greater the viscosity (less stratification), the more readily they break (E. B. 

 Harvey, 1945). 



Parthenogenesis. — MgClg added to sea water, used first by Morgan (June, 1899, 

 1900 a, b) for parthenogenesis, then by Loeb (October, 1899, 1900 a, b) ; plutei first 

 obtained by Loeb (1899; see Loeb 1913a, p. 53, 57, etc.). R. S. Lillie (19 10, 1911a, 

 1914a) found isotonic MgClg did not activate. HoUingsworth (1941) obtained slight 

 parthenogenesis with isotonic MgCla, but inhibition of its activation by CaClj. 



Other Species (additional) and General References 



Bialazewicz, 1927, 1929. A. pustulosa (lixula) and Paracentrotus lividus, electrolytes. 



Heilbrunn, 1952, p. 528. General Physiology, general. 



Herbst, 1904. Saks necessary for development. 



Loeb, 1913 a. Artificial Parthenogenesis, especially for S. purpuratus and S. franciscanus. 



Robertson and Webb, 1939. Amount of Mg in sea water and body fluids. 



Rothschild and Barnes, 1953. P. lividus, amount in egg; table of salts and species. 



Wilson, 1901a. Toxopneustes {Lytechinus) variegatus, cytology. 



