ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 647 



ments, it is extremely hard to avoid an infection of the eggs 

 by sperm. I proceeded as follows in the experiments with 

 Chsetopterus. As soon as the animals were brought into the 

 laboratory by the collector, the tubes in which they live were 

 opened and the worms removed. As soon as the first female 

 was found it was put into a special dish and thoroughly 

 washed off with sea-water, the water being renewed from six 

 to twelve times in succession. The sea-water in the labora- 

 tory was found to be absolutely free from spermatozoa of 

 Chsetopterus. (The animals are found on the beach of an 

 island at some distance from the laboratory.) After the 

 female had undergone the process of washing, it was exposed 

 to a current of sea- water over night to remove as far as pos- 

 sible any spermatozoa that might have been left on the sur- 

 face. The next day the animal was ready to be used for an 

 experiment. On that day and before the experiment began, 

 the experimenter did not bring his hands in contact with 

 any other Chsetopterus or with the aquarium that contained 

 such animals. His hands and instruments were sterilized 

 with fresh water. The posterior part of the animal which 

 contains the eggs was cut off and thoroughly washed for two 

 minutes in distilled or fresh water. Had any spermatozoon 

 been left on the surface of the animal, the distilled water 

 would have killed it. After this the part containing the eggs 

 was put into a vessel with sterilized sea-water, washed off 

 once more and then put into another dish containing steril- 

 ized sea-water. In this dish the single parapodia were 

 opened successively, the eggs sucked out from each with a 

 pipette, and then collected in another dish with sterilized 

 sea-water. After all the eggs had been collected they were 

 divided into two lots. The one lot remained in normal 

 (sterilized) sea-water, to serve as control material. The 

 other lot was distributed into the various solutions whose effect 

 I intended to test. In no case did I see a single egg of tJte 



