ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 661 



(1) 5 c.c. 2$n KC1 + 95 c.c. distilled water 



(2) 10 " + 90 



(3) 15 " + 85 



(4) Normal sea-water (control) 



The eggs were left in these solutions seven minutes and 

 were then put back into sterilized sea-water. The next 

 morning about 1 per cent, of the eggs that had been in 

 solution 1 were swimming about. The eggs that had been 

 in solution 2 had practically all reached the larva stage, 

 although not all of them were swimming. The eggs that 

 had been in the third solution contained swimming larvae, 

 but fewer than the other two lots. The control eggs had 

 remained absolutely urisegmented during the first nine to 

 ten hours. They showed, however, a beginning of segmen- 

 tation (2-3 cells) the next morning. 



Sixteenth series. There was no longer any doubt 

 concerning the fact that KC1 is able to bring about the 

 development of the unfertilized eggs of Chsetopterus. It 

 was, moreover, apparent from experiment 10 that if only 

 ic.c. 2^nKCl is added to 99^c.c. of sea-water, no trocho- 



W tw 



phores are formed. It was natural to conclude from this 

 that a certain minimal amount of K ions must enter the egg 

 in order to make it reach the trochophore stage. In order to 

 decide this the following experiment was tried. The eggs 

 of one female were put into a solution of 2 c.c. 24 n KC1 + 

 98 c.c sea- water, and put back into normal sea- water at 

 various intervals, viz., after one minute, three minutes, seven 

 minutes, nine minutes, thirteen minutes, twenty minutes, 

 forty minutes. The results of this experiment were as defi- 

 nite as could be desired. 



After from nine to ten hours the eggs of the first lot (that 

 had been in the KC1 sea- water for one minute only) were 

 absolutely unsegmented. In the second lot (three minutes) 

 a few eggs were segmented, but no trochophore was formed. 



