Regeneration 191 



when subsequently transferred back to normal sea water. 

 Such eggs will develop when fertilized with sperm. 

 The activating effect of the membrane formation has, 

 therefore, been reversed and the eggs have gone back 

 into the resting stage. 1 Wasteneys has found that the 

 rate of oxidation which was raised considerably by the 

 artificial membrane formation goes back to the value 

 characteristic for the resting eggs after the reversal 

 of their developmental tendency. 2 Similar results 

 were obtained in eggs activated with NH 4 OH. It 

 appears from this as though the change in the cortical 

 layer which leads to the development of the egg and 

 the increase in the rate of oxidations were reversible 

 in the egg of Arbacia. 3 



The writer had previously noticed that eggs of 

 Strongylocentrotus purpuratus, which had been treated 

 for two hours with hypertonic sea water, not infrequently 

 began to divide into two, four, or eight cells (and some- 

 times more) and then went back into the resting state 

 (except that they possessed the second factor required 

 for development as stated in Chapter V). It may be 



1 Loeb, Arch.f. Entwcklngsmech., 1914, xxxviii., 277. 



2 Wasteneys, H., Jour. Biol. Chem., 1916, xxiv., 281. 



3 F. Lillie thinks that the KCN in this experiment merely inhibits the 

 change of the cortical layer necessary for development. This is con- 

 tradicted by two facts: first, the writer has shown in 1906 that KCN docs 

 not inhibit the membrane formation, and, second, the eggs will not 

 return to the resting stage when put back into sea water too soon; in 

 that case they will disintegrate. This shows that in the KCN something 

 more happens than the mere block to disintegration. 



