328 GRACE MEDES 



of the hydroxyl and the hydrogen ions on account of the mixed 

 phosphates and carbonates which it contains, whereby addition 

 of acid or alkah brings about a readjustment of the equiUbrium 

 instead of a corresponding wide swing in the concentration of the 

 hydrogen and hydroxyl ions. They found that a disturbance of 

 the equiUbrium toward the acid side was much more harmful 

 than toward the alkaline, since addition of alkali or of alkaline 

 salts such as di-sodic phosphate in small amounts produced a 

 beneficial effect upon growth, whereas acids or acid-salts were 

 from the start inhibitory in their action. The concentration 

 of the hydrogen and the hydroxyl ions seemed to be the deter- 

 mining factor in development, while the action of the cation en- 

 tered as a specific factor only in case the hydrogen and hydroxyl 

 concentrations were low, as with the phosphates of the alkalies. 

 Loeb ('06) placed newly fertilized eggs of Strongylocentrotus 

 lividus in neutral van't Hoff solution and found that none 

 developed beyond the four- to eight-cell stage. Addition of 

 0.1 cc. N/100 KOH to 50 cc. of the solution allowed a few eggs 

 to reach the blastula stage; addition of 0.2 cc. allowed 60 per 

 cent to reach the gastrula stage and 0.4 and 0.8 cc. N/100 KOH 

 to 50 cc. permitted all to develop into larvae. With greater 

 concentrations of the hydroxyl, the eggs were more or less in- 

 jured, until in 0.8 cc. N/100 KOH none could segment. He did 

 not, however ('13), believe the rate of development affected, as it 

 was not noticeably raised by the addition of 0.5 cc. or 0.7 cc. 

 N/10 NaOH to a neutral solution of M/2 (NaCl -f- KCl -f 

 CaCl2). The increased rate of oxidations in the presence ol 

 excessive amounts (more than 0.8 cc. N/10 NaOH to 50 cc. of 

 the neutral solution) "suffices to suppress the development of 

 the egg" and hence ''cannot be utihzed for any conclusions upon 

 the normal oxidations in the sea-urchin egg." 



METHODS 



The experimental work for this paper was done at Woods 

 Hole, Massachusetts, during the summers of 1914 and 1915. In 

 the first year, the experiments were carried on during the latter 

 part of July, all of August and early September, and in the 



