STUDIES IN ARTIFICIAL PARTHENOGENESIS. 361 



toxicity is due to the lower surface tension possessed by pure 

 water (see p. 350). The experiments of R. Lillie have often been 

 adduced as evidence in favor of the "theory of antagonism." 

 Lillie's results find a most suitable explanation when the surface 

 tension of the solutions is considered (see p. 351). A recent paper 

 by Lillie 1 seeks to show an antagonism between salts and anses- 

 thetics in their action on starfish and sea-urchin eggs. This 

 would seem to contradict the results gained in this paper. All 

 that Lillie show r s, however, is that various anaesthetics, such as 

 ether, chloroform, etc., exert a slight protective influence on 

 eggs partially cytolyzed with isotonic NaCl solution. This pro- 

 tective action is probably due to the effects of the anaesthetics 

 upon the bacteria which are always found to infest cytolyzing 

 eggs. When these are killed the egg is able to live longer. 

 Gorham and Tower 2 showed that sea-urchin eggs could be kept 

 in healthy condition in sterile sea-water for II days or longer, 

 whereas they soon disintegrate if exposed to bacteria. 



SUMMARY. 



1. All known methods of producing an elevation (formation) 

 of the vitelline membrane in the egg of the sea-urchin result in a 

 lowering of surface tension. 



2. The following substances, all of which lower surface tension, 

 were also found effective in producing membrane elevation: 

 acetone, chloretone, urethane, chloral hydrate, methyl acetate, 

 ethyl butyrate, methyl salicylate, acetamide, picric acid. 



3. A simple physical explanation of the process is given, which 

 is based on Fol's original interpretation. 



I desire to express my sincere thanks to Prof. B. F. Kingsbury 

 of Cornell University for helpful advice in the preparation of this 

 paper. Thanks are also due to Prof. W. D. Bancroft, who has 

 been consulted on several questions of a chemical nature. 



1 R. S. Lillie, Amer. Journ. Physiol., XXX., I (1912). 



2 F. P. Gorham and R. \V. Tower, Amer. Journ. Physiol., VIII., 175 (1902). 



