428 Ralph S. Lillie 



tripling the velocity of the process or combination of processes on 

 which the initiation of development depends. The process of 

 membrane-formation shows a similarly high temperature-coeffi- 

 cient of acceleration. 



3 The responsiveness of eggs to this treatment varies greatly 

 at different periods in the life of the egg. Warming within five 

 minutes after the removal of the eggs from the animal is ineffective, 

 and has the effect of preventing permanently the dissolution of the 

 germinal vesicle. Warming at any time between the beginning 

 of nuclear dissolution and the separation of the first polar body 

 may result in development and the production of larvae; the most 

 favorable period is some little time (lo to 20 minutes) before the 

 separation of the first polar body. Warming subsequently to this 

 event tends to produce abnormal form changes or irregular cleav- 

 age; after maturation is complete the effect is mainly to acceler- 

 ate the coagulative change characteristic of mature unfertilized 

 eggs in presence of oxygen. 



4 Maturing eggs placed in ^^o KCN solution retain for several 

 hours their susceptibility to development by the above means. A 

 stay of a certain duration in cyanide solution followed by momen- 

 tary warming in this solution and transfer to sea-water is followed 

 by a striking increase in the proportion of favorably developing 

 eggs. Further exposure of eggs to cyanide solution for a certain 

 period after warming effects a still further improvement in the con- 

 ditions of parthenogenetic development. Eggs thus treated with 

 cyanide approximate closely, in the rate, character, and favorability 

 oftheir development, to normally fertilized eggs. 



5 Since the essential action of the above dilute cyanide solutions 

 is to prevent intracellular oxidations, the inference is drawn that 

 anaerobic processes play an important part in the series of changes 

 leading to the initiation of development in starfish eggs. Sup- 

 pression of oxidative combined with acceleration of hydrolytic and 

 reducing processes is indicated as a condition of the initiatory 

 process in these eggs. 



