Nature of the Process of Fertilization 121 



technical side of the experiments will find all the necessary data 

 in my publication in the American Journal of Physiology} 

 Here I wish only to mention the following points: 



1. These experiments were made after the spa^\Tiing season 

 was practically over. 



2. Bacteriological precautions were taken against the possi- 

 bility of contamination of the hands, dishes, or instruments 

 with spermatozoa. 



3. The spermatozoa contained in the sea-water lose, accord- 

 ing to the investigation of Gemmill,^ their fertilizing power 

 within five hours if distributed in large quantities of sea- water. 



4. We have a criterion by which we can tell whether the 

 egg is fertilized or not in the production of a membrane. The 

 fertilized egg forms a membrane and the unfertilized egg has no 

 distinct membrane. None of the unfertilized eggs that devel- 

 oped artificially had a membrane.^ 



5. With each experiment a number of control experiments 

 were made. Part of the unfertilized eggs were put into the 

 same normal sea-water that was used for the eggs that did 

 develop. None of these eggs that remained in normal sea-water 

 formed a membrane or showed any development, except that a 

 few of them were divided into two cells after about twenty- 

 four hours. 



6. I made another set of control experiments by putting a 

 lot of eggs of the same female into a solution w^hich differed less 

 from the normal sea-water than the one which caused the 

 formation of blastulae or plutei from the unfertilized eggs. 



1 Loeb, J., "On the Artificial Production of Normal Larvae from the Unferti- 

 lized Egg of the Sea-Urchin," Amer. Joum. of Phys., III. 



2 Gemmill, "The Vitality of the Ova and Spermatozoa of Certain Animals," 



Joum. of Anat. and Phys., 1900. 



3 The method used in these experiments was primitive inasmuch as no ferti- 

 lization membrane was formed. A few years later I found a method for the 

 artificial production of a fertilization membrane, which is described in the next 

 paper. In the earlier experiments in which no fertilization membrane was 

 developed, nevertheless a change in the cortical layer of the egg was brought 

 about by the combined action of the hydroxyl-ions of the solution, and the 

 increased osmotic pressure. 



