158 L. V. HEILBRUNN. 



DIAMETER OF EGGS IN A. 

 65 

 65 

 66 

 66 

 66 

 66 



DIAMETER OF EGGS IN B. 



63 n X 63.5 M at 10.04 A.M. 



63 63 at 10.05 A.M. 



64 65 at 10. 06 A.M. 



63 64 at 10. 06 A.M. 



64 65 at 10.07 A.M. 



62 65 at 10.08 A.M. 



63 63.5 at 10.08 A.M. 



62 62 at 10.09 A.M. 



63 63.5 at 10.10 A.M. 

 63.5 64 at 10. ii A.M. 



64 65 at 10.34 A.M. 

 63.5 63.5 at 10.35 A.M. 

 63.5 66 at 10.36 A.M. 

 63.5 65 at 10.37 A.M. 



63 63.5 at 10.38 A.M. 

 62 66 at 10.39 A.M. 



64 64 at 10.40 A.M. 

 63.5 65 at 10.41 A.M. 

 63.5 64 at 10.41 A.M. 

 63.5 65 at 10.42 A.M. 



Average 63.7 /j.. 



In this experiment also only eggs from a single female were 

 used. The untreated eggs measured 72/4 x 73^1, 72^1 x 73, 7iju x 

 73M. 7I-5M x 74/z, 7i.5/zx73/z. Considering the eggs as spher- 

 ical, their average diameter was 72.4^. Thus on the average, 

 the diameter of the eggs in A decreased 5-9/i, whereas the diame- 

 ter of the eggs in B decreased 8-7/i. Thus exosmosis was much 

 more pronounced in the solution which caused membrane swelling 

 than in a solution of equivalent concentration in which this 

 effect was lacking. 



II. CORTICAL CHANGES. 

 A. Membrane Elevation and Membrane Swelling. 



When the sea-urchin sperm comes in contact with the egg, 

 almost immediately the vitelline membrane is lifted away from 



