STUDIES IN ARTIFICIAL PARTHENOGENESIS. 355 



(and oxygen) in lowering surface tension has already been dis- 

 cussed. 



KCN. Dilute potassium cyanide is practically equivalent to 

 KOH + HCN, as it undergoes hydrolysis. Hence, the state- 

 ments in regard to alkalis apply also here. 



Metallic Copper or Silver. Herbst 1 found that membrane elev- 

 tion was induced by the presence of metallic Cu or Ag. His 

 results were confirmed by Matthews, 2 whose experiments how- 

 ever were performed on starfish eggs. Herbst used silver reduced 

 from silver nitrate, and also a silver coin. In the former case,- 

 silver nitrate is probably present and effects a precipitation of 

 chlorides with a consequent dilution of the sea-water and an 

 exchange of chlorides in solution to nitrates. (For a considera- 

 tion of the effects of dilution, and of the relative effects of vari- 

 ous ions, see p. 350.) In the latter case, it is necessary to note 

 that all silver coins are alloys of copper, a metal which Matthews 

 finds to be much more potent than the silver coin itself. 3 The 

 action of copper is due to the fact that this metal is attacked by 

 NaCl in the presence of air. As a result of this reaction copper 

 oxychloride is formed and the solution becomes alkaline. 4 Thus 

 the action of copper is a special case of the action of alkalis, and 

 the metal does not produce an "action at a distance," as Matt- 

 hews supposes. 



Electric Current. Although an electric current has been used 

 by Schiicking and McClendon, neither of these authors states 

 whether membrane elevation occurs. In both cases, copper 

 wires were probably used, so that membrane elevation may have 

 been induced by the action of copper itself, as shown above. 



Oocytin. This is an hypothetical substance isolated by T. B. 

 Robertson 5 from blood serum and from sperm. Although called 

 a "fertilizing agent" it produces normal membrane elevation 

 on "sensitized" eggs only. On " unsensitized " eggs it produces 



1 C. Herbst, Mitth. a. d. zool. Station z. Neapel, XVI., 445 (1904). 



2 A. P. Matthews, Amer. Journ. Physiol., XVIII., 39 (1907). 



3 Metallic silver may itself react for NaCl in the presence of oxygen changes it 

 into AgCl with the simultaneous formation of NaOH. (See Gmelin-Kraut, Lehr- 

 buch der anorg. Chemie, II. (2), p. 26.) This reaction probably takes place very 

 slowly, however. 



4 Tilden, Soc. Chem. Ind., V., 84 (1886). 



6 T. B. Robertson, Arch. f. Ent. Mech., XXXV., 64 (1912). 



