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.’ 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. Ihave 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 
Cheetopterus experiment (see p. 649), although my precautions 
were vastly superior to those taken by Viguier. 
1 Part IT, p. 539, 
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