Fertilization and Oxidation 35 



beyond the four- to eight-cell stage. Addition of . 1 c.c. N/100 

 KOH allowed a few eggs to reach the blastula stage; addition 

 of . 2 c.c. N/100 KOH allowed 60 per cent to reach the blastula 

 stage and with 0.4 and 0.8 c.c. N/100 KOH all the eggs 

 developed into larvae. 



If we add more KOH to 50 c.c. of the van't Hoff solution, 

 we find that the addition of 0.4 c.c. N/10 KOH interferes 

 already with their development; if we add 0.8 c.c. ,N/10 KOH, 

 or more, to 50 c.c. van't Hoff solution, no egg can segment.' 



If one wishes to obtain the best type of larvae it is better 

 to add varying concentrations of NaHCOs. If to 50 c.c. of the 

 neutral van't Hoff solution are added 0, . 1, . 2, . 4, . 8, 1.0, 

 2.0 c.c. m/20 solution of NaHCOs; in the solution without and 

 with only . 1 c.c. NaHCOs only early segmentations take place; 

 in all the otiier solutions the eggs will develop into larvae. In 

 the solution with 1.0 c.c. or more NaHCOj the eggs already 

 suffer. 



It seems that the faintly alkaline solution is chiefly necessary 

 only for the first development of the eggs of purpuratus. Later 

 they are able to develop in a neutral but not in an acid solution. 

 The lowest Cho for the development of the egg of Arbacia at 

 Woods Hole is about lO"-^" N, i.e., these eggs can begin to 

 develop not only in a neutral but even in a faintly acid solu- 

 tion. This difference between the two kinds of eggs may 

 be of some importance in regard to the difference in their 

 response to the agencies of artificial parthenogenesis, as we 

 shall see later. 



The writer pubhshed years ago a paper in which he showed 

 that the development of the eggs of Arbacia is retarded and 

 finally inhibited if increasing quantities of acid are added to 

 the sea-water. He has since vainly attempted to show that 

 the rate of development of the sea-urchin egg can be increased 

 with the increase of the concentration of hydroxylions in the 



1 Loeb, Biochem. Zeiischr., II, 88, 1906. 



