ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 651 
1 and 2 developed into trochophores, very few of the eggs of 
solution 4 and none of solution 3 reached the trochophore 
stage. The control eggs remained undeveloped. 
Fourth series.—The results were obviously puzzling if 
the increase of the osmotic pressure was the only factor that 
brought about the development of the unfertilized eggs of 
Cheetopterus. But they would be intelligible if there were, 
in addition to the effect of an increase in the osmotic pres- 
sure, a specific effect of the KCl or the K ions. In order 
to decide this, the unfertilized eggs of a female were dis- 
tributed into the following solutions: 
(1) 5cc. 24x KCl +95 cc. sea-water 
(2) 10 “ (79 +90 “ 
(8) 15 “ 6c + 85 (73 
(4) 5 “ NaCl+ 95 «“ 
(5) 10 “ “ + 90 “ 
(6) 15 “ : “ce + 85 Ts 
(7) Normal sea-water (control) 
The eggs remained one hour in these solutions. 
The next day the control eggs (7) were undeveloped. 
The eggs that had been in the first three solutions were 
teeming with trochophores. In lots 4 and 5 nota single 
swimming trochophore was found, although many eggs had 
begun to develop. The development stopped, however, in 
an early stage. Of the eggs that had been in solution 6 a 
large number had reached the trochophore stage and were 
swimming. These results were as clear as could be desired. 
In order to bring about artificial parthenogenesis through 
the addition of NaCl, 15 ¢.c. of the 24m solution had to be 
added, while 5 c.c. of a 24n KCl solution were sufficient. 
Fifth series.—There was a possibility that the effect pro- 
duced by NaCl was a specific Na effect, and not an effect of 
the increase in osmotic pressure. An experiment with cane- 
sugar could decide this question. My stock solution of 
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