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. sea-water-+ 
1.0c¢.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.! 
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.? 
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 weber kiinstliche Parthenogenese, p. 369, Leipzig, 1906. 
2 Loeb, op. cit. 
