STUDIES IN ARTIFICIAL PARTHENOGENESIS. 



333 



My experiments with Cumingia eggs show clearly that after 

 fertilization not only do the eggs swell more rapidly in hypotonic 

 solutions but their total imbitition of water is greater. 



Five minutes after fertilization some eggs were placed in 25 

 c.c. sea-water plus 15 c.c. distilled water. At the same time some 

 unfertilized eggs were placed in a similar solution. Both sets of 

 eggs were measured after about 45 minutes. By this time the 

 eggs had reached an osmotic equilibrium for a second set of 

 measurements 45 minutes later showed no further change. The 

 results are given in Table II. 



TABLE II. 



DIAMETERS OF FERTILIZED AND UNFERTILIZED EGGS IN 25 c.c. SEA-WATER + 15 



c.c. DISTILLED WATER. 



Average Diameter of 12 Unfertilized Eggs in Sea-water 62.65 p.. 



Measurements were made with a Spencer movable scale 

 micrometer at a magnification of about 650 diameters. Not all 

 the fertilized eggs remained spherical. For such eggs the longest 

 and shortest diameters are recorded on the table. In computing 

 the averages the mean of these two measurements was taken. 

 It is obvious from the table that a greater amount of water 

 entered the fertilized eggs. This can not be explained by assum- 

 ing an increased permeability to water. 



It should be noted that the vitelline membranes of the eggs in 

 this experiment did not rupture as a result of being placed in the 

 hypotonic solution. Such a rupture sometimes occurs in solu- 

 tions of this strength. 



