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 3 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. In case 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 



