STUDIES IN ARTIFICIAL PARTHENOGENESIS. 319 



As in Arbacia the Cumin gia vitelline membrane is capable of 

 two kinds of cortical change. Both membrane elevation and 

 membrane swelling can occur. If the egg is placed in solutions 

 of low surface tension the tension of the membrane is lowered 

 and it rapidly lifts away from the egg. No doubt the explanation 

 of this process is the same as that I have offered for the similar 

 process in the sea-urchin egg. But in Cumingia membrane 

 elevation is not the normal cortical change. When eggs are 

 inseminated the membrane does not become elevated, it becomes 

 swollen. 



Treatment of eggs with a reagent which causes either mem- 

 brane elevation or membrane swelling will result in a throwing 

 off of polar bodies. Thus just as in the sea-urchin egg either 

 swelling or elevation provides the necessary cortical change, 

 although in this egg it is swelling and not elevation which is 

 normal. Finally there is a third way in which maturation can 

 be initiated. This consists in the removal of the membrane. 



I shall now proceed to the experimental data considering first 

 membrane elevation, second membrane swelling, and third the 

 removal of the membrane. 



MEMBRANE ELEVATION. 



Any substance which markedly lowers the surface tension of 

 sea-water is effective in producing membrane elevation. But if 

 elevation is to be followed by maturation only certain concentra- 

 tions and certain lengths of exposure can be used in each case. 

 Too high a concentration or too long an exposure generally leads 

 to coagulation. Frequently an over-exposure produces a rupture 

 of the egg membrane, the protoplasm then flows out to form an 

 exovate. Such eggs soon disintegrate. 



Numerous reagents were used to produce a lowering of surface 

 tension. Of course the number of successful reagents could have 

 been increased many fold. Thus many of the higher alcohols 

 no doubt act in the same way as the amyl alcohol which I used. 



In the experiments the same general proceedure was always 

 employed. In every case, the eggs of only a single female were 

 used. Owing to the fact that the number of eggs obtainable 

 from a single female is comparatively small, I found it best to 



