STUDIES IN ARTIFICIAL PARTHENOGENESIS. 349 



due to a reaction or reactions brought about by the escape of CC>2 

 as a result of increased permeability. Unfortunately, however, 

 he does not bring up any evidence in favor of this accessory 

 hypothesis, and it is, indeed, difficult to understand how both 

 reaction and swelling can take place in so short a time. 



The appended list is an enumeration of all the various methods 

 by which membrane elevation may be artificially induced in sea- 

 urchin eggs. Sometimes artificial parthenogenesis has been de- 

 scribed without any records to show if membrane elevation 

 occurred. Several of these methods are included in the list, 

 where they are followed by a question mark. Most acids only 

 cause membrane elevation after the eggs have been restored to 

 normal sea-water, but in all other cases the process occurs 

 directly. 



f Chloroform (Hertwig). 



I Toluol, benzol, xylol, oil of cloves, creosote (Herbst). 

 So-called lipoid solvents ~i , 



Ether, alcohol (Matthews). 



I Amylene, phenol (Loeb). 

 Distilled water (Schiicking). 

 Dilution of sea-water (Schiicking). 

 Isotonic NaCl, KC1 (Lillie). 

 Soap (Loeb). 



Saponin, digitalin, solanin (Loeb). 

 Bile salts (v. Knaffl-Lenz). 

 Sea- water charged with CCh (Delage, Lyon). 

 Passage of hydrogen and oxygen (Matthews). 

 Shaking (?) (McClendon). 

 Heat (34 Loeb) (32 (?) McClendon). 

 Alkalis (Loeb, Schiicking). 

 KCN (?). 



Metallic copper or silver (Herbst). 

 Electric current (?) (Schiicking). 

 Blood serum (Loeb). 

 Oocytin (Robertson). 

 Higher fatty acids (Loeb). 

 Lower fatty acids (Loeb)^ 



Hydroxi-acids (Loeb), /-Membrane elevation only after return to sea-water. 

 HNO 3 and HC1 (Loeb), J 



I shall now attempt to prove that every known method of 

 producing membrane elevation results in a lowering of the surface 

 tension of the liquid surrounding the egg. Proceeding in order, 

 the first class of substances noted are those often grouped as 



