ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 659 



The eggs that had been in solution 1 had very few swim- 

 ming trochophores, those that had been in solutions 2 and 3 

 had many, and those that had been in solution 4 still more. 

 The control eggs were mostly undeveloped; a small number 

 were segmented into from 2 to 16 cells. 



Twelfth series. In the experiments thus far mentioned 

 a 2^ n KC1 solution had been added to normal sea- water. 



M 



As the osmotic pressure of the sea-water is about equal to 

 that of a | n KC1 solution, in all these experiments with KC1 

 there was a rise in the osmotic pressure of the sea-water. I 

 now wished to try whether this increase in osmotic pressure 

 is essential for the KC1 effect, or whether a mere increase in 

 the number of K ions without an increase in the osmotic 

 pressure of the sea-water is able to bring about the par- 

 thenogenetic development of the eggs of Chsetopterus. The 

 solutions used were as follows: 



(1) 2 c.c. 2J KC1 +91 c.c. sea-water + 7 c.c. distilled water 



(2) 3 +86 +11 " " 



(3) 2 +98 



(4) 3 +97 



(5) 5 " MgCl 2 +95 



(6) Normal sea-water (control) 



The eggs remained in the solution fifty-five minutes. 

 Nine hours later (the same evening) swimming trochophores 

 were found in those that had been in the first four solutions. 

 The eggs that had been in the other two solutions were 

 entirely undeveloped. Some had been left permanently in 

 these solutions. Some of those left in solutions 1 and 2 had 

 reached the trochophore stage and were swimming about. 



The next morning these results were confirmed. Fully 

 one-third of all the eggs that had been fifty-five minutes in 

 solutions 1-4 swam about as trochophores. Those that had 

 been in solutions 5 and 6 had not reached the trochophore 

 stage; only a few eggs had begun to segment. 



