652 STUDIES IN GENERAL PHYSIOLOGY 



cane-sugar was a 2n solution, while my NaCl solution was 

 2 \n. On account of the electrolytic dissociation, more than 

 30 c.c. of the cane-sugar solution were required to produce 

 the same increase of osmotic pressure as by 15 c.c. of the 

 2^n NaCl solution. The following solutions were tried : 



(1) 40 c.c. 2n cane-sugar +60 c.c. sea-water 



(2) 20 " " +80 " 



(3) 10 " +90 



(4) 10 2itiKCl +90 " 



(5) Normal sea-water (control) 



The eggs remained fifty-five minutes in these solutions. 

 Eight hours later swimming ciliated trochophores were found 

 in the eggs that had been in solutions 1 and 4. In 2 and 3 

 there were no swimming larvae. In the control material all 

 the eggs were still spherical and unsegmented. The next 

 morning about 25 per cent, of the eggs that had been in 

 solution 1 swam about in the most lively manner. A few 

 trochophores were found among the eggs that had been in 

 solution 2. But the control eggs and the eggs that had 

 been in solution 3 had in the best case only reached the 

 earliest stages of segmentation. This leaves no doubt that 

 an increase in the osmotic pressure of the sea-water is 

 sufficient to bring about artificial parthenogenesis in the 

 eggs of Chsetopterus. 



Sixth series. In order to make this conclusion stronger, 

 it was necessary to try the effect of an increase in the osmotic 

 pressure of the sea- water by the addition of still other sub- 

 stances. The following were tried: 



(1) 5, c.c. 5n CaCl 2 +95 c.c. sea-water 



(2) 10 " " +90 " 



(3) 10 2JwMgCl 2 +90 



(4) 20 " " +80 



(5) 30 " " +70 



(6) Normal sea-water (control) 



