Artificial Parthenogenesis in Starfish Eggs 415 



An experiment of August 17 showed a similar result: Eggs placed 

 ten minutes after removal in 2^/017 KCN, left in this solution two 

 hours, then washed for 10 minutes in normal sea-water and 

 warmed, gave a considerable number of larvae. 



In these experiments the eggs were not warmed directly in the 

 cyanide solution; but were first transferred to normal sea-water 

 and theii after an interval, subjected to the warming process in 

 the latter medium. The largest proportion of larvae developed 

 from eggs warmed within 15 minutes to half an hour after this trans- 

 fer (Experiments 2 to 4) ; later the conditions became less favorable- 

 The failure to reach advanced stages in Experiments 5 and 6 may 

 seem to contradict the rule found above that optimal conditions 

 for parthenogenesis are found at a time approaching that of the 

 separation of the first polar body. The influence of the cyanide 

 must, however, be taken into account; as will be seen later the 

 presence of cyanide during the warming process improves the 

 conditions greatly, and the greater favorabihty in the earlier 

 experiments in all probabihty depends on the relative briefness 

 of the period succeeding removal from the cyanide solution. These 

 eggs were thus exposed at a relatively favorable stage of matura- 

 tion while still to a certain degree under the influence of the cyanide. 

 Such a combination of circumstances would be favorable to devel- 

 opment. 



In the experiments now to be described the eggs were exposed 

 to the high temperature while in the cyanide-containing sea-water. 

 In the first series they were placed in ^f^-^ KCN solution at an early 

 maturation stage, and after varying intervals were warmed to 35° 

 for 70 seconds in the same solution and then transferred directly to 

 sea-water. The result has appeared uniformly that under such 

 conditions a far larger proportion of eggs develop, and develop- 

 ment is more rapid and more nearly normal, than in eggs warmed 

 in normal sea-water without the cyanide treatment. 



