INITIATION OF DEVELOPMENT IN NEREIS. 1 3 



the action of KCl every egg maturates but never more than one 

 in a thousand swims. If the eggs be allowed to remain in sea- 

 water from two to twelve hours with frequent changes of sea 

 water the results are about the same. Dry eggs subjected to 

 KCl treatment maturate, cleave once or twice, and produce, in 

 one experiment at least, seven per cent, of swimming forms made 

 up of unsegmented two and four-cell "swimmers." 



The Experiments. 



5, 10, 15, 20 and 25 per cent. 2.5M KCl were used. It was 

 found^ that 15 per cent. 2.5M KCl in sea-water gave the best 

 results. Typical experiments follow: 



(a) August 12, 10:54 A.M. Lot A : Eggs from two females cut 

 in 80 c.c. of 20 per cent. 2.5M KCl at 10:54. Lot 5: Eggs from 

 one dry female put in 3 c.c. of 20 per cent. 2.5M KCl. At ii :oo 

 jelly formation in both. Samples of eggs taken from A and B 



as follows: 



No. 1 11:00 



No. 2 11:10 



No. 3 11:17 



No. 4 11:25 



No. 5 11:33 



No. 6 11:40 



No. 7 11:50 



No. 8 12:00 



August 13, 12:00 M. Dry eggs of August 12 (Lots A and B), 

 All maturated ; some cleavage-like processes and some swimming 

 forms after twenty minutes' exposure or more. Highest per- 

 centage (five) of swimmers after fifty minutes' exposure. These 

 are unsegmented, two and four-cell swimmers. 



(b) August 12, 12:05 P.M. Water changed three times on 

 eggs during three hours and then placed in 20 c.c. of 20 per cent. 

 2.5 M KCl in sea-water. Samples taken at five-minute intervals 

 up to 1:00 P.M. 



August 13, 1:00 P.M. Washed eggs of August 12, all matur- 

 ated; I in 1,000 swim. 



Experiments during August 13 and 14 with fifteen per cent. 

 2.5 M KCl gave about the same results. 



(c) August 15, 9:30 A.M. Two females quickly cut in 10 c.c. 



