ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 657 
cent. KCl is added to sea-water the unfertilized eggs of 
Cheetopterus throw out their polar bodies, while the addition 
of 4 per cent. NaCl to sea-water produces no such effect. 
It seemed of interest to find out whether the K ions were 
possibly able to cause the parthenogenetic development of 
Chetopterus larve without the osmotic pressure of the sea- 
water being raised. 
Ninth series.—-The following mixtures were prepared: 
(1) 10 cc. 24 KCL+ 90 c.c. sea-water 
(2) 5 “ we + 95 “ 
(8) 24 x3 ‘79 + 98 (zs 
(4) Normal sea-water (control) 
The eggs remained in the solutions one hour. The sea- 
water used had been sterilized by heating it to a temperature 
of 80° C., as in all the previous experiments. 
The next morning each of the first three lots contained a 
large number of free swimming larve, while the control 
material contained none. 
Tenth series.—I intended to find out the minimum amount 
of KCl necessary to bring about artificial parthenogenesis. 
Moreover, I wished to know whether the addition of KCl to 
sea-water did not act more quickly upon the eggs than an 
increase in the osmotic pressure by some other substance. 
Seven solutions were used: 
(1) dec. 24n KCl +993 c.c. sea-water 
(2) 1 ce “cc +99 oy 
(3) 2 66 6 +98 6“ 
(4)10 “ “ +90 @ 
(5) 1 “ NaCl+99 “ 
(6) 2 “cc “cc +98 “ 
(7) Normal sea-water (control) 
One lot of eggs remained in these solutions from five to 
ten minutes, the others from sixty to seventy minutes. 
The results were as follows: None of the two lots that had 
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