642 STUDIES IN GENERAL PHYSIOLOGY 



(1.) 100 sea-water + 25 2 n cane-sugar 

 (2.) 82J sea-water+17i 2$n urea 



Both the sugar solution as well as the urea solution injured 

 the eggs, the urea solution much more than the sugar solu- 

 tion. I made an attempt to produce parthenogenesis by 

 submitting unfertilized eggs to a pure cane-sugar solution 

 whose osmotic pressure was about equal to that of the sea- 

 water, to 90 c.c. of which 10 c.c. of a 2^n NaCl solution had 

 been added. When the unfertilized eggs of Arbacia were 

 put for about two hours into a mixture of 60 2 n cane-sugar 

 + 40 distilled water or 55 2n cane-sugar + 45 distilled 

 water, many of them segmented and a few developed into 

 swimming blastulse, but they died within the first twenty- 

 four hours. This proves conclusively that the development 

 of the unfertilized egg is produced through an increase in 

 the concentration of the surrounding solution. As it is 

 immaterial whether the increase in the osmotic pressure is 

 brought about by electrolytes or non-conductors, there can 

 be no doubt that the essential feature in this increase in the 

 osmotic pressure of the surrounding solution is a loss of 

 water on the part of the egg. 



5. Having reached the conclusion that the loss of water, 

 or rather the loss of a certain amount of water, causes the 

 parthenogenetic development of the egg, it seemed possible 

 to take another step in advance. In all the previous experi- 

 ments the unfertilized eggs had been submitted to a solution 

 of higher osmotic pressure for from one to two hours, and 

 were then put back into normal sea-water to develop. If 

 the initial loss of water on the part of the egg were all that 

 is required for the . production of artificial parthenogenesis, 

 it would be possible to find a solution which would not only 

 take away water from the egg, but which would also allow 

 development to go on. I remembered from my earlier 

 experiments on the effects of an increase in the concentration 



