IMMUNITY' AND SUSCEPTIBILITY OF SEA-URCHIN EGGS. 237 



would have the same effect in increasing the pressure abnormally 

 and causing a fall in immunity at the same time, which it does 

 not do. Hence from this, together with the evidence, in other 

 instances, of H acting differently than do other ions, and the 

 probability that the dissolution of the nuclear membrane is caused 

 or accompanied by chemical changes, it may be inferred that the 

 H ions have a specific chemical effect, which, in addition to their 

 electronic action, accounts for the fall in immunity at about 30' 

 after fertilization. 



Both series of experiments agree, however, in making the 

 period of greatest susceptibility just at the beginning and during 

 the earlier part of cleavage, though for the HC1 this drop seems 

 to come somewhat earlier than for ether. The explanation for 

 this effect of HC1 we believe to be essentially the same as for that 

 of ether, viz., that the H ions in some way penetrating the mem- 

 brane cause a repulsion of at least the cytoplasmic particles, 

 thereby augmenting the normally increased pressure to such an 

 extent that further development is inhibited. 



EXPERIMENTS WITH KC1, NaCl AND Na CITRATE. 

 The acceptance of a specific action for the ions is, of course, 

 by implication not limited to H, but is quite as necessary for 

 others, like K, Na, Ca, etc. For instance Loeb in one place 

 holds that the kations (specific) and not the anions are poison- 

 ous, 1 for the reason that the newly fertilized Fundnlus egg will 

 develop in KC1 but not in NaCl ~ and because, of fertilized Arbacia 

 eggs in |-# NaCl only 10, 20, and in one case 50 per cent, be- 

 gan to segment, the majority stopping in the 2-cell stage, while 

 in ^u KC1, 7080 per cent, segment to 8 cells. 3 Opposed to 

 this view of Loeb's is that which ascribes toxic effects also to the 

 anion, for, e. g., NaCl, NaBr, Nal and NaFl have a different poi- 

 soning effect. The two views, however, are quite compatible if 

 the colloids affected are in the two cases of different sign. Loeb 

 also finds that the toxic effects of Na salts is a function of the 

 valency, increasing from the acetate to the citrate. 4 Further- 



1 Loeb, Am. Jour, of Physiology, III., VII. and VI., VI. and Archh- fiir d. 

 ges. PA}>siot.,Rd. 88, 1901. 



2 Loeb, Am. Jour, of Physiology, III., VIII. 



3 Loeb, Am. Jour, of Physiology, III., IX. 



4 Am. /'itr. of Physiology, VI., VI. 



