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 24n KCl solution had been added to normal sea-water. 
As the osmotic pressure of the sea-water is about equal to 
that of a 3n KCl solution, in all these experiments with KCl 
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 KCl 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 Chetopterus. The 
solutions used were as follows: 
(1) 2cc.24n KCl +91 c.c. sea-water+ 7 c.c. distilled water 
(2) 3 a ee + 86 “ + 11 66 (73 
(3) 2 iT3 ce + 98 [73 
(4) 3 «6 497 “ 
(5) 5 “ MgCl, +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. 
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