598 STUDIES IN GENERAL PHYSIOLOGY 
ination of the sea-water with spermatozoa. As a rule, I 
proceeded in the following way. The unfertilized eggs of 
one female were divided into three or more lots. One lot 
was put into the artificial solution by which I hoped to cause 
the development of the unfertilized eggs. The second lot 
was put into normal sea-water to serve as a test or control 
for the presence of spermatozoa in the sea-water. The third 
lot was put into an artificial solution which as a rule differed 
less from the normal sea-water than the solution which 
caused the development of the egg. Whenever the eggs of 
one lot were put back into normal sea-water, the eggs of 
the other lots were put into the same sea-water. Thus all 
three lots of eggs were kept in sea-water of exactly the same 
degree of contamination. In no case did a single egg of 
the three lots form a membrane. No egg of lot 2, which 
remained in normal sea-water all the time and served as a 
test for the presence of spermatozoa, showed any develop- 
ment except a beginning of segmentation (2-3 cells) after 
about twenty hours. In no case did any of the eggs of lot 
2 or 8 develop into a blastula. 
The chief sources of infection in such experiments are 
the instruments and the hands of the experimenter if he 
opens male and female animals at the same time. The dishes 
in my experiments were cleaned with fresh water, in most 
cases the evening before the experiment was made. The 
instruments which were used had been cleaned in fresh water 
and kept dry for twenty-four hours. Incase the first animal 
opened was a male the instruments were laid aside, the hands 
disinfected, and new instruments used for the next animal. 
It happened that in almost every one of the following ex- 
periments the first animal I opened was a female, and thus 
the chief danger of contamination by spermatozoa was 
naturally avoided. 
But even if the experiments had not been carried on with 
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