FK UTILISATION OF THE EGGS OF ANIMALS. 155 



spermatozoa were swimming. If the eggs excrete an 

 attracting substance it was argued that it should be present 

 in the tubes, and the spermatozoa should collect there. 



In order to make certain that the eggs had i-emained 

 normal during their stay in the sea-water, just before filtra- 

 tion some of the eggs were tested by ai-tificial fertilisation. 

 In all the experiments upon which reliance has been placed 

 for results this took place in the normal manner, i e. the 

 vitelline membrane became raised. The first stages of 

 segmentation were also often watched, and found in the 

 majority of cases to follow the usual plan. The eggs were 

 also tested soon after they had been placed in water. If, as 

 rarely happened, they did not become fertilised readily they 

 were rejected. The experiments were repeated with four 

 sets ((J and ?) of Arbacia, three of Sphaer echinus, and 

 two of Echinus. 



No attraction of the spermatozoa into a tube could be 

 observed. Except for a surface-contact phenomenon to be 

 further discussed, they went in and out with indifference. 

 Apparently, therefore, the water which had contained the 

 eggs exercised no directive stimulus on the spermatozoa 

 whatever. 



I then attempted to find some substance which would give 

 a chemotactic stimulus to the spermatozoa. The substances 

 tested were such as are known to give a directive chemical 

 stimulus to many protozoa, the spermatozoa of ferns, pollen- 

 tubes, etc. The following solutions were tried by the capillary 

 tube method : distilled water ; meat extract 1 per cent. ; 

 potassium nitrate 10 per cent., 2 per cent. ; sodium chloride 

 5*8 per cent., 2"9 per cent., 0-58 per cent.; potassium nialate 

 1 per cent., O'l per cent.; asparagin 1 per cent.; glycerine 

 5 c.c. per cent.; grape sugar 18 per cent., 9 per cent., 4*5 

 per cent., 2*25 per cent. ; peptone 1 per cent. ; alcohol 50 per 

 cent., 25 per cent., 10 per cent.; diastase (from Merk) 1 per 

 cent. ; oxalic acid O'O percent., O'OO per cent., 0"009 percent. ; 

 nitric acid (concentrated) 1 per cent., O'l per cent., O'Ol per 

 cent. 



