THE FERTILIZATION-REACTION IN EC HI N A- 

 RACHNIUS PARMA. VIII. 



Fertilization in Dilute Sea-water. 



E. E. JUST.i 

 Rosenwald Fellow in Biology, National Research Council. 



The writer has shown, 2 by means of experiments made in 1920 

 at the Marine Biological Laboratory, Woods Hole, Mass., that a 

 given dilution of sea- water with tap water which leaves the unin- 

 seminated egg of Echinarachnius parma intact is rapidly injurious 

 to the inseminated egg during its process of membrane separation. 

 After membrane separation the egg is likewise resistant to the 

 action of the dilute sea- water. Certain experiments were also 

 made during the same season to learn if it is possible to procure 

 fertilization and development in diluted sea-water to which the 

 inseminated egg during membrane separation is susceptible. 

 These experiments were repeated during May and June of the 

 1921 season at the laboratory with essentially the same results. 



In experiments made to discover if in a given dilution of sea- 

 water, which is injurious to the inseminated egg of Echinarachnius 

 during the period of membrane separation, it is possible to fer- 

 tilize the egg, it was soon apparent that cleavage and normal gas- 

 trulation are not possible in a dilution which permits membrane 

 separation. Thus during the period June 21 to June 28, 192 1, 

 inclusive, eggs from twenty-four females were inseminated in 

 normal sea- water and in sea-water of varying dilutions. In all 

 cases due precautions were taken as to the bulk of eggs, quantity 

 of solution, and density of the sperm suspensions used in order 

 that as far as possible conditions be made uniform. The results 

 obtained with 95 per cent, sea-water (95 parts sea-water plus 5 

 parts tap water) and the dilutions ranging from this to 80 per cent, 

 sea- water (80 parts sea- water plus 20 parts tap water) may be 



1 Zoological Laboratory, Howard University. 



2 Am. Jour. Phys., 1922, 61, 516. 



