.Artificial Parthenogenesis 105 



completely and swell enormously. In solutions of the 

 mineral acids no membranes are formed and none are 

 formed as a rule when the eggs are transferred back to 

 sea water. When both a mineral and a lower fatty acid, 

 e. g.y butyric, are added to sea water the mineral acid 

 acts as if it were not present, i. e., the eggs form mem- 

 branes when transferred back to sea water if the con- 

 centration of the butyric acid is high enough. All 

 these data are comprehensible if we assume that only 

 that part of the acid causes membrane formation which 

 is lipoid soluble, while the water soluble part is not 

 involved in the process of membrane formation; and 

 that the cytolysis or swelling of the whole egg can only 

 take place in the higher fatty acids (heptylic or above) 

 which are little soluble in water and very soluble in 

 lipoids, while the lower fatty acids, whose water solubil- 

 ity is comparatively high, can only bring about a cyto- 

 lysis and swelling in the cortical layer but not in the 

 rest of the egg. This makes it appear as though the 

 part undergoing an alteration in membrane formation 

 was a lipoid ; and this would harmonize with the assump- 

 tion that the specific membrane-inducing substance 

 in the spermatozoon is not soluble in water, but soluble 

 in fat. 



4. These and other observations led the writer to 

 the view that the essential process which causes de- 

 velopment might be an alteration of the surface of the 

 egg, in all probability an alteration of the superficial 



