ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 653 
The eggs remained in these solutions one hour, and were 
then put back into normal sea-water. I neglected to look 
at them the same evening. The next morning I found a 
small number of swimming larve among the eggs that had 
been in solution 5 (80 c.c. 24n MgCl, +70 c.c. sea-water). 
The control eggs were undeveloped; the Ca, eggs had gone to 
pieces. The experiment demonstrated only that the increase 
of the osmotic pressure through MgCl, can bring about the 
development of the unfertilized eggs of Cheetopterus. 
Seventh series. —I suspected that my failure to get swim- 
ming trochophores from a mixture of sea-water and a 5n 
CaCl, solution might have been due to the poisonous effect 
of the calcium, having noticed in my previous experiments 
on the artificial parthenogenesis in sea-urchins that the par- 
thenogenetic larve produced by the addition of CaCl, to sea- 
water soon died. I therefore started a new experiment early 
in the morning and watched the eggs during the day. I 
found indeed that an increase in the osmotic pressure of the 
sea-water by the addition of CaCl, leads to the formation of 
swimming trochophores from the unfertilized eggs of Cheetop- 
terus. The solutions used were as follows: 
(1) 24 cc. 5” CaCl, + 97% c.c. sea-water 
(2) 5 “ “ +95 os 
(8) 10 ‘73 [73 + 90 ce 
(4) 15 “ct “ + 85 (73 
(5) 20 2in MgCl, +80 
(6) Normal sea-water (control) 
The eggs were exposed to these solutions for fifty minutes. 
After nine hours the eggs that had been in solution 3 con- 
tained living trochophores which died during the night. 
None of the other solutions gave rise to swimming trocho- 
phores. 
Eighth series.—As there was no more doubt left that: the 
increase in the osmotic pressure of the sea-water or the loss 
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