ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 657 



cent. KC1 is added to sea-water the unfertilized eggs of 

 Chastopterus throw out their polar bodies, while the addition 

 of i 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 

 Ch?etopterus larvas without the osmotic pressure of the sea- 

 water being raised. 



Ninth series. The following mixtures were prepared: 



(1) 10 c.c. 2|w KC1 + 90 c.c. sea-water 



(2) 5 " " +95 " 



(3) 2fc " +98 



(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 larvas, while the control 

 material contained none. 



Tenth series. I intended to find out the minimum amount 

 of KC1 necessary to bring about artificial parthenogenesis. 

 Moreover, I wished to know whether the addition of KC1 to 

 sea-water did not act more quickly iipon the eggs than an 

 increase in the osmotic pressure by some other substance. 

 Seven solutions were used: 



(1) ^ c.c. 2^n KC1 + 99ic.c. sea-water 



(2) 1 +99~ " 



(3) 2 " " +98 



(4) 10 +90 " 



(5) 1 " NaCl + 99 " 



(6) 2 +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 



