ASTIFICIAL 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 larvae among the eggs that had 

 been in solution 5 (30 c.c. 2^n MgCl 2 +70 c.c. sea-water). 

 The control eggs were undeveloped ; the Ca 2 eggs had gone to 

 pieces. The experiment demonstrated only that the increase 

 of the osmotic pressure through MgCl 2 can bring about the 

 development of the unfertilized eggs of Chsetopterus. 



Seventh series. I suspected that my failure to get swim- 

 ming trochophores from a mixture of sea- water and a 5w 

 CaClg 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 larvae produced by the addition of CaCl 3 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 2 leads to the formation of 

 swimming trochophores from the unfertilized eggs of Chsetop- 

 terus. The solutions used were as follows: 



(1) 2J c.c. 5n CaCl 2 + 97f c.c. sea- water 



(2) 5~ " " +95 



(3) 10 " " +90 " 



(4) 15 " " +85 " 



(5) 20 2iwMgCl a + 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 



