570 FRANK R. LILLIE 



merited with the spermatozoa of sea-urchins by the method of 

 Pf eff er and came to the conclusion that ' ' the spermatozoa of the 

 Echinoidea are not attracted to the egg by means of any special 

 substance excreted by the latter. The vast number of spermato- 

 zoa and the large size of the eggs are sufficient to ensure the neces- 

 sary contact taking place." Von Dungern ('02) also rejects' 

 the idea of an egg-secretion attracting the spermatozoa in the 

 case of sea-urchins and starfish. Morgan, Payne and Brown 

 ('10) also accept Puller's interpretation, and there has recently 

 been a tendency among biologists to reject chemotaxis of the 

 spermatozoon as a factor in the fertilization of the egg. 



Previous observers have worked either with Pfeffer's capillary 

 tube method, or with the eggs themselves. I made a sufficient 

 number of experiments with capillary tubes to convince myself 

 that this method of experimentation is many times less effective 

 than the method I employed. As illustration: July 4, 1912: 

 I filled three pieces of capillary tubing with a concentrated solu- 

 tion of CO 2 in sea-water, with 10 per cent and 1 per cent of this 

 solution and broke off short pieces — neither end of which had 

 been in the solution — to be tested. These pieces were then intro- 

 duced into an active sperm suspension of Nereis beneath a raised 

 cover-slip. In the course of a few minutes a decided positive 

 reaction was obtained with the first and second tubes, the sperm 

 appeared to stream into the open mouth of the capillary tubes and 

 soon formed white plugs at the mouths of the tubes. The tube 

 containing 1 per cent CO 2 sea-water and a control tube with sea- 

 water alone showed no reaction. In a repetition of this experi- 

 ment the 1 per cent CO 2 sea-water and control were negative, and 

 the 10 per cent showed only slight reaction. The diameter of 

 the lumen of the tube was 0.48 mm. A much finer tube of 10 

 per cent CO2 sea-water showed no reaction at all. With tubes of 

 the size first used 10 per cent CO2 sea-water is near the minimum 

 for a positive reaction. But a drop of 0.5 per cent CO2 sea-water 

 injected into a similar suspension causes chemotactic response. 

 Tubes of the size used are therefore about twenty times less effec- 

 tive as indicators of the chemotactic reaction, stated in terms of 

 percentage of CO 2 required, than the injected drop method. It 



