650 STUDIES IN GENERAL PHYSIOLOGY 



All the sea- water had been sterilized the previous day by 

 heating it to a temperature of 80 ; one part (a) of the eggs 

 remained one hour, a second part (6) one hour and twenty 

 minutes in these solutions. 



The first four solutions yielded numerous swimming 

 trochophores ; their number was greatest in the first two 

 solutions. Lot a of the MgCl 2 solution yielded no swimming 

 blastulse, but lot 6 had a few. The control eggs were com- 

 pletely undeveloped, with the exception that after about ten 

 hours a few showed the beginning of a segmentation, which 

 in no case led to the formation of more than from 4 to 6 

 cells. During the next forty-eight hours no further develop- 

 ment occurred, and the eggs died and disintegrated. Accord- 

 ing to this experiment the unfertilized eggs of Chaetopterus 

 are not able to develop in normal sea-water. They can, 

 however, be caused to develop into trochophores if exposed 

 for about an hour to sea-water whose concentration has been 

 raised through the addition of the right quantity of KC1 or 

 NaCL 



Third series. The next task was to ascertain how much 

 the osmotic pressure of the sea-water must be raised in 

 order to bring about the parthenogenetic development, and 

 whether the increase in osmotic pressure necessary for this 

 purpose was the same in each case. The solutions used 

 were as follows: 



(1) 10 c.c. 2n KC1 +90 c.c. sea-water 



(2) 12i c.c. 2fn KC1 +87J 



(3) 30 c.c. 2 n cane-sugar + 70 " 



(4) 12J c.c. 2n NaCl +87J " 



(5) Normal sea-water (control) 



The osmotic pressure in solutions 2, 3, and 4 was about 

 the same. The eggs remained sixty-five minutes in these 

 solutions, and were then put back into normal sea-water. 

 While a great number of the eggs that had been in solutions 



