540 STUDIES IN GENEEAL PHYSIOLOGY 



(Arbacia) proceeded best in MgCl 3 , next best in KC1, while 

 CaClg proved to be the most injurious in the series. 



Seven years ago I, and later Norman, found that if the 

 concentration of sea-water be raised sufficiently by the addi- 

 tion of certain salts, a segmentation of the nucleus takes 

 place without any segmentation of the protoplasm. Such 

 eggs, however, when brought back into normal sea-water, 

 divide into as many cells as there are preformed nuclei. 

 This year I tried the effects of equimolecular solutions of 

 MgCl 2 , KC1, NaCl, and CaCl 2 upon this process of nuclear 

 division (in which the nuclear membrane is apparently 

 liquefied), and found that the influence of the four salts 

 (or rather kations) followed the order mentioned above. 



We know that enzymes as a rule require a slight degree 

 of acidity or alkalinity for their action. I showed last year 

 that the addition of a small amount of H ions to sea-water 

 retards or prevents segmentation, while a small amount of 

 HO ions favors and accelerates the development of the Arbacia 



egg- 



2. It has been known for some time that the unfertilized 



eggs of echinoderms, worms, and arthropods begin to seg- 

 ment when left for a comparatively long time in sea-water. 

 This has generally been considered a pathological phenom- 

 enon. Mead succeded in causing a segmentation of the 

 unfertilized egg of a marine worm, Chsetopterus, by the addi- 

 tion of a very small amount of KC1 to sea-water. Morgan 

 tried the effect of more concentrated sea-water on the un- 

 fertilized egg of sea-urchins, with results similar to those 

 obtained by me previously with the same methods in fer- 

 tilized eggs. If the unfertilized eggs are brought back from 

 the more concentrated sea-water into normal sea-water, they 

 break up into as many cells as there are nuclear masses pre- 

 formed in the more concentrated solution. But in none of 

 these cases did the cell-divisions of the unfertilized eggs lead 



