164 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



The following experiment, in which sea-w r ater was used instead 

 of the van't Hoff solution, is also instructive. Eggs were used 

 for which the concentration of the hydroxylions in sea-water 

 was not high enough to permit of their development. To 50 c.c. 

 of sea-water 4, 8, 12, 16, 24, and 32 c.c. 2J m NaCl solution 

 were added, and some of the eggs of one female were divided 

 among these solutions. After 20, 40, 70, 100, 135, 210, 273, and 

 346 minutes portions of the eggs were replaced in normal sea- 

 water. In no case did even a single egg develop to a larva. 

 Many eggs started cleavage; but this soon ceased, a fact to 

 which we shall return later. It might have been supposed that 

 here one was dealing with eggs which could not be caused to 

 develop in any way at all by the osmotic effect. However, it 

 was possible to show that it depended upon too low a concentra- 

 tion of hydroxylions. Thus a control experiment was per- 

 formed, in which 0, 0. 1, 0.2, 0.4, and 0.8 c.c. of N/10 NaOH 

 were added to 50 c.c. of van't Hoff's solution +16 c.c. of 2J m 

 NaCl and some of the eggs of the same female were divided 

 among these solutions. After 30, 60, 90, 120, and 210 min- 

 utes portions of these eggs were transferred to normal sea- 

 water. Of the eggs treated with neutral van't Hoff's solution 

 not a single one developed into a larva, while the eggs treated 

 for 90 to 120 minutes with alkaline solution produced larvae; 

 the larvae were most numerous in that portion of the eggs 

 which had been for 90 minutes in the solution with 0.8 c.c. 

 N/10 NaOH. Of this portion 80 per cent of the eggs devel- 

 oped into larvae. 



On the other hand it was possible to show that in hyper- 

 alkaline solutions a relatively small increase of the osmotic 

 pressure was sufficient to cause the formation of larvae in 

 unfertilized eggs, and that any further increase of osmotic pres- 

 sure only diminished the time of exposure to the solution neces- 

 sary for the formation of larvae. The following experiment will 

 serve as an example. To 50 c.c. of the van't Hoff solution + 



