ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 649 



once started an experiment, although I knew that it was 

 practically impossible to exclude contamination by sperma- 

 tozoa if I attempted to isolate the eggs immediately after 

 having handled a male. The female was washed off in steril- 

 ized sea-water, but of course I was aware that this would 

 not suffice to get rid of any spermatozoa that might be stick- 

 ing to the surface of the animal. The eggs, however, were 

 taken and distributed into the following five solutions: 



(1) 6 c.c. 2n KC1+94 c.c. sea-water 



(2) 8 " +92 



(3) 10 " +90 " 



(4) 12 " +88 " 



(5) Normal sea-water (control) 



One part of the eggs remained one hour and twenty-five 

 minutes, the rest one hour and forty minutes in the solu- 

 tions. The experiment was started in the afternoon. The 

 next morning 1 I found numerous swimming larvse (trocho- 

 phores) in the material that had been in the first four solu- 

 tions for one hour and twenty-five minutes. In the second 

 lot they were less numerous. But even in the control 

 material I found two swimming trochophores. It followed 

 that the Chsetopterus were either naturally parthenogenetic or 

 the precautions against the entrance of spermatozoa had not 

 been sufficient. 



Second series. From now on I applied the rigid anti- 

 septic measures against spermatozoa described above in the 

 introduction. The following solutions were used: 



(1) 8 c.c. 2Jw KC1 +92 c.c. sea-water 



(2) 10 c.c. 2nKCl +90 



(3) 12c.c.2i^KCl +88 



(4) 12 c.c. 2n NaCl +88 



(5) 20 c.c. 2|nMgCl 2 +80 



(6) Normal sea-water (control) 



1 1 shall in the following descriptiou of the experiments consider only whether 

 or not swimming trochophores were formed. The morphological details will be 

 given in section v. It goes without saying that all the experiments deal with unfertil- 

 ized eggs, unless the contrary is distinctly stated. 



