136 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



Before going farther, we should point out that the minimal 

 value of concentration for an acid to prove effective is not quite 

 the same for eggs of different females. In my experiments upon 

 the causation of development of sea-urchin eggs by means of 

 the blood serum of warm-blooded animals, it has been an ever- 

 recurring observation that these experiments only succeed for 

 a part of the eggs of a female, unless the eggs are previously 

 sensitized by a treatment with SrCl 2 (see chap, xviii). I 

 regard the variation in permeability of the eggs of different 

 females to acids or blood as responsible for these individual vari- 

 ations. The mass of the eggs also exerts some influence. If 

 too many eggs are placed in the solution, the stated mass of 

 acid is not enough. 



Overton observes that the narcotic effect of the dihydric 

 alcohols is much weaker than that of the monohydric alcohols. 

 I find that the monobasic acids of the former series exhibit a 

 much weaker effect with regard to membrane formation than the 

 corresponding members of the series of acids of the monatomic 

 alcohols. I may quote as evidence experiments with oxypro- 

 pionic and oxybutyric acids. 



TABLE XXI 



It will be seen from a comparison between this and the pre- 

 ceding table that |3-oxybutyric acid possesses only a quarter of 

 the efficiency of butyric acid, and that propionic acid is more 

 than four times as effective as lactic acid. The oxy-acids also 



