ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 685 



cally, and that it is only due to the constitution of the sea- 

 water (or blood?) if they do not do so under natural con- 

 ditions. 1 It might be that the constitution of the sea-water 

 at Algiers differs from that of the rest of the world, and 

 allows the eggs of the sea-urchin to develop parthenogenetic- 

 ally. The experiments of Mr. Viguier are, however, not 

 of such a character as to make this probable. They are few 

 in number, and he seems to have omitted no possibility 

 which could further the contamination of his eggs by sper- 

 matozoa. He always handled males and females together, 

 and opened males and females in the same experiment. No 

 mention is made of a sterilization of his hands or instruments. 

 Whenever males and females are in the same dish there is 

 danger that the water may be full of spermatozoa, especially if 

 the material is fresh. The sperm sticks to the surface of the 

 females and it is absolutely impossible to avoid fertilization 

 of the eggs. To be sure, Viguier mentions a precaution he 

 took, but this precaution shows that he is not familiar with 

 the methods of sterilization or disinfection. He washed the 

 females off in filtered sea-water. As everybody knows, the 

 spermatozoa go through filter paper, and, in addition, sea- 

 water does not remove the spermatozoa from the surface of 

 the female, for the latter stick to solid bodies, as Dewitz has 

 proved. In order to avoid this source of infection I washed 

 the surface of the female several minutes in distilled water, or 

 under a powerful stream of fresh water which kills the sper- 

 matozoa. I have in my former papers given a description of 

 the precautions necessary in experiments on parthenogene- 

 sis. These were by no means exaggerated if one wished to 

 guard absolutely against contamination. I did not even 

 succeed in excluding contamination by spermatozoa in my first 

 Chaetopterus experiment (see p. 649), although my precautions 

 were vastly superior to those taken by Viguier. 



i Part II, p. 539. 



