98 FERTILIZATION 



all, as Loeb pointed out in 19 14. Calcium is also involved in the 

 maturation of marine eggs ; this has been noted in several different 

 sorts of immature eggs, as Table 15 shows. 



TABLE IS 

 Presence of Ca in the external medium necessary for the induction 



of maturation 



Calcium is necessary for the discharge of the cortical granules 

 in the sea-urchin egg (Moser, 1939^) ; for the transformation of the 

 isotropic cortical granules into birefringent rods while in the peri- 

 vitelline space (Endo, 1952); and for the tanning of the fertiliza- 

 tion membrane (Hobson, 1932^), though for reasons discussed in 

 chapter i, this may be another and less detailed way of express- 

 ing Endo's observation. In addition, Hultin (1949, 1950^,6) has 

 made an interesting series of studies on the effects of adding calcium 

 to sea-urchin egg homogenates prepared in Ca-free media. His 

 main findings were that, after adding CaCU, there was : 



(i) A rapid uptake of Oo, without a corresponding increase in 

 CO2 evolution, for twenty minutes. Cyanide did not inhibit the 

 reaction. 



(2) No breakdown of carbohydrate. 



(3) Inhibition of the reaction after treatment of homogenates 

 for thirty minutes with 0-005 M-monoiodoacetate. 



(4) Granular components in the homogenates, including yolk 

 globules, disintegrated explosively and there was a marked in- 

 crease in the viscosity of the whole system. Note, Echinochrome 

 granules, which are freely distributed in the cytoplasm of the un- 

 fertilized egg of Arbacia punctulata, move into the cortex after 

 fertilization, arriving there about ten minutes after fertilization 

 (E. N. Harvey, 19 10). Heilbrunn (1934) showed that these pig- 

 ment granules disintegrate explosively in the presence of free 

 calcium or magnesium, the former being a hundred times as 



