414 Ralph S. LiUie 



was first tested. Sea-water containing KCN in 3^^^ to —-^^ con- 

 centrations acts in the same manner as sea-water deprived of its 

 dissolved oxygen by a current of hydrogen or otherwise; the mat- 

 uration process is checked, and may be resumed on retransfer to 

 sea-water if too long an interval has not elapsed. As shown above, 

 after the maturation-process has progressed beyond a certain 

 stage, starfish eggs become less and less susceptible to the influence 

 of momentary warming. It can be shown that the process (what- 

 ever its nature) which deprives the egg of this susceptibility is 

 retarded or prevented along with the maturation by the addition 

 of cyanide to the sea-water. This is illustrated by the following 

 experiments: 



Eggs were placed August 21, 1907, 20 to 25 minutes after 

 removal from the animal, in sea-water containing ywo KCN. In 

 this solution they were left for 2 h. 30 m. They were then trans- 

 ferred to normal sea-water (which was changed to free the eggs of 

 adhering cyanide) and portions were warmed to 35° for 70 seconds 

 at successive intervals of ten minutes until the appearance of the 

 first polar body. At the close of the period of exposure to the 

 cyanide solution the eggs were almost all in an early maturation 

 stage with invisible germinal vesicle. Maturation was resumed 

 in normal sea-water; the polar bodies began to separate after an 

 interval of i h. 30 m.; a certain delay in the resumption of the 

 process is thus indicated. Eggs were warmed at the following 

 intervals after return from cyanide solution to normal sea-water 

 and the results were as tabulated in the following table: 



TABLE VII 



