STUDIES OF FERTILIZATION. 137 



7. Effects oj H and OH Ions on Copper Inhibition. 



Two series of experiments (Nos. 24 and 25) were run to see if 

 increase in H or OH ions protected against the inhibitory action 

 of copper chloride. As might have been expected, increase in 

 acidity of the sea-water had no favorable effect. On the alkaline 

 side some protective action is found between about 1/2,500 

 N NaOH and 1/666 N NaOH by volume. In the best case 

 about 33 per cent, of the eggs segmented when 1/666 N NaOH 

 was added to 1/500,000 copper chloride sea- water. The mem- 

 branes were, however, very narrow, and the cells tended to 

 separate in cleavage owing to this fact. The appearance of the 

 eggs was similar to eggs segmenting in a copper solution too 

 weak to produce complete inhibition. The effect was no doubt 

 due to precipitation of some of the CuCl 2 as Cu(OH) 2 , but the 

 dissociation of the copper salts was still sufficient to inhibit very 

 greatly. 



8. The Protective Action of Gum Arabic and Gelatin Against 

 Copper. 



Egg-water stands by no means alone in protecting against the 

 inhibiting action of copper on fertilization. The same result 

 may be obtained with either gum arabic or gelatin, and pre- 

 sumably with other colloids and proteins. 



The protective action of gum arabic begins at 0.2 per cent, 

 and becomes complete at 0.8 per cent, (see Table V.). As the 

 gum arabic has no deleterious action of its own it furnishes 

 complete protection at the proper concentration, as the table 



shows. 



TABLE V. 



(Exp. 32.) PROTECTIVE ACTION OF GUM ARABIC. Identical inseminations in 



the fluids (a) to (e) and their controls. (One drop of i : 25 : 7.5 c.c.) 

 One Part of CuCl 2 Per Cent. Same Solutions Without Per Cent, 



to 500,000 Parts of of Eggs CuCh (Controls). Segmented. 



Segmented. 



(a) 0.2% gum arabic in s.w 10% (a) 0.2% gum arabic in s.w 100% 



(b) 0.4% gum arabic in s.w 55% (b) 0.4% gum arabic in s.w 100% 



(c) 0.8% gum arabic in s.w. . ..100% (c) 0.8% gum arabic in s.w 100% 



(d) 1.6% gum arabic in s.w 100% (d) 1.6% g".m arabic in s.w 100% 



(e) Sea-water (copper control) . . o Sea-water only 100% 



The protective action of gelatin begins at 0.008 per cent, and 

 becomes complete at 0.064 P er cent, (see Table VI.). 



