ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 663 
next morning, after they had been in these solutions for 
twenty-four hours, the first solution contained many eggs 
in the beginning stages of segmentation but not one swim- 
ming larva could be discovered. The second and third 
solutions contained a large amount of swimming larve; in 
the second they were more numerous than in the third. In 
the control material only a few eggs began to segment; no 
swimming larve were to be found. Thisconfirmsour former 
observation that an addition of $c.c. 24n KCl to 994 ce. 
sea-water is insufficient to produce parthenogenesis, while 
the addition of 1 KCl is sufficient. 
Eighteenth series.— There is something paradoxical in 
the fact that the addition of 2 cc. 24 » KCl to 98 ec. sea- 
water can produce parthenogenesis in three minutes, while 
the addition of $c.c. 24n KCl to 994 cc. sea-water cannot 
accomplish the same result in twenty-four hours. Before I 
accepted this as a fact I wished to see it confirmed once 
more. The same solutions were applied as before: 
(1) dec. 24n KCl 995 c.c. sea-water 
(2) 1 «4-99 es 
(3) 1b # 4983 : 
(4) Normal sea-water (control) 
Part of the eggs were put back into normal (sterilized) 
sea-water after thirty minutes, while the others remained in 
the solution during the next twenty-four hours. As far as 
the latter are concerned the results were exactly like those 
described in the preceding experiment. The eggs that had 
remained in solution 1 over night had not developed beyond 
the early cleavage stages. No egg had reached the trocho- 
phore stage. In the second solution a large number of swim- 
ming larve were found, and in the third solution they were 
numerous. About 75 per cent. of all the eggs were in the 
trochophore stage, and many of these were swimming about. 
The eggs that had remained in these solutions only thirty 
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