Artificial Parthenogenesis in Starfish Eggs 387 



ever mature eggs are treated in such a way as to form fertilization 

 membranes — whatever method is used — a certain proportion are 

 always found to undergo cleavage. Another observation that I 

 have frequently made appears to favor the idea that there is a cor- 

 relation between membrane-formation and the acceleration of oxi- 

 dation processes in the egg. I have found uniformly that the coagu- 

 lation and disintegration which follow when mature eggs are allowed 

 to remain for some hours in normal oxygen-containing sea-water, 

 occur much more rapidly in eggs that have formed membranes 

 than in those that remain without this structure. Thus, warming 

 eggs during early maturation to 35° for 25 or 30 seconds induces 

 membrane-formation in a large proportion — usually about one- 

 half — but not in all of the eggs; practically all of the eggs so treated 

 die at an early stage ; if they are examined after 1 8 hours, those with 

 membranes are invariably found to be in an advanced state of 

 disintegration, the entire space enclosed by the membrane being 

 filled with a mass of loose granular detritus; those without mem- 

 branes, on the other hand, although coagulated and opaque, are 

 still compact and undisintegrated. The same contrast between 

 eggs with and without membranes in the rate and character of the 

 disintegration is seen when the membranes are formed by the 

 action of ether or a fatty acid. This result, which I have found 

 with perfect uniformity throughout the present investigation, 

 shows that eggs which have formed membranes, yet without under- 

 going normal development, exhibit less resistance to the disinte- 

 grative action of the post-maturation oxidative changes than do 

 those lacking these formations. It is possible that the greater 

 cytoplasmic activity of the eggs with membranes (as shown by the 

 production of pseudopodia and the irregular cleavages and other 

 form-changes) may facilitate the disintegrative process; the effect 

 may also conceivably be dependent, at least in part, on simple 

 mechanical conditions: the change in the closely adhering surface- 

 layer of the unaltered egg, due to the removal of the membrane- 

 forming substance, would probably facilitate the action of any 

 disintegrative agency. One might suggest that the mechanical 

 resistance to surface-changes, including cleavage, is lessened by 

 the formation of a membrane, and that the significance of the 



