642 STUDIES IN GENERAL PHYSIOLOGY 
(1.) 100 sea-water+25 2n cane-sugar 
(2.) 824 sea-water-+173 24n 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 24n NaCl solution had 
been added. When the unfertilized eggs of Arbacia were 
put for about two hours into a mixture of 60 2n cane-sugar 
+40 distilled water or 55 2n cane-sugar+45 distilled 
water, many of them segmented and a few developed into 
swimming blastule, 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 
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