212 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



This action of bases upon the swelling and liquefaction of the 

 membrane of Lottia takes place only in the presence of oxygen. 

 If the oxygen was removed, the eggs of Lottia kept their 

 chorion and their irregular outline, even if they remained for 

 from four to six hours in alkaline sea-water (50 c.c. sea-water + 

 l.Oc.c. N/10 NaOH). If the eggs were afterward placed in 

 oxygenated alkaline sea-water the chorion dissolved and the 

 eggs could be fertilized by sperm. The addition of KCN to 

 the hyperalkaline sea-water also prevented the dissolution of 

 the chorion. 1 



We are forced to assume that in our original method of 

 artificial parthenogenesis the hypertonic solution combined two 

 effects, the membrane formation and the corrective effect. The 

 membrane formation was atypical, since it only led to the forma- 

 tion of a gelatinous film around the egg, but it was the essential 

 feature. It seems to the writer to be of great interest that a 

 hypertonic solution will also cause the swelling and liquefaction 

 of the chorion of Lottia. 2 



Finally we have seen that benzol causes membrane forma- 

 tion in the sea-urchin egg; it also causes the liquefaction of the 

 chorion of Lottia. 



Acid did not dissolve the chorion of Lottia, nor will it cause 

 parthenogenesis in Lottia either. Acids, however, dissolve the 

 chorion of the sea-urchin egg, as Herbst first observed. 



All these facts led the writer to speculate as to whether 

 the cortical layer of the unfertilized egg does not contain a 

 substance similar to that of which the chorion of these eggs 

 consists; that the membrane formation is only the expression 

 of the swelling and liquefaction of this colloidal substance, and 

 that the swelling and liquefaction of this substance is the 

 prerequisite which allows the egg to develop. 



5. In my experiments I have often had the opportunity of 

 observing membrane formation in eggs that were not spherical 



1 Loeb, Untersuchungen ueber kunstliche Parthenogenese, p. 369, Leipzig, 1906. 



2 Loeb, op. cit. 



