NOTES ON THE PHYSIOLOGY OF FUCUS- SPERMATOZOIDS. 1 29 



zoids would be less active and no accumulation would occur. At 

 the time the work was done the relation between toxicity and 

 chemotaxy was not considered and further work on this phase 

 was not attempted. It would appear that the subject should be 

 investigated. 



EXPERIMENTS ON PHOTOTAXY. 



That Fucus spermatozoids are negatively phototactic is very 

 evident. Under the microscope the large majority will be 

 observed to swim away from the light and in a short time prac- 

 tically all the active spermatozoids will be found on the side 

 away from the light. If a capillary tube lies parallel to the window 

 the spermatozoids in the drop will collect against the tube on the 

 window side, blocked in their movement away from the light. 

 If mounted on a slide containing a bright spot of light in a dark 

 field, there is no collection in the bright area as Englemann (4) 

 found for Euglena under the same conditions. The spermatozoids 

 pass in and out of the bright area with no apparent response. 



A slide holding a drop of sea water one fourth inch in di- 

 ameter was placed about two feet from a north window. In less 

 than five minutes practically all the active spermatozoids were 

 found crowded on that side of the drop away from the window. 

 It seemed possible this might be due to gravity. 



Two slides were arranged as above, one inclined toward the 

 window and one tilted away from it. In both cases the sper- 

 matozoids were found crowded on the side away from the 

 window. In both cases the spermatozoids swam away from the 

 light, but in one case they swam with gravity and in the other 

 against gravity. A liter beaker half filled with sea water yello\v 

 with spematozoids was set on a shelf ten feet from a north win- 

 dow. In ten minutes far more active spermatozoids were found 

 in a drop taken from the side away from the window than were 

 found on the lighted side. 



INFLUENCE OF TEMPERATURE ON ACTIVITY. 



From indications during the experiments on chemotaxy it was 



observed that temperature had a very considerable effect on the 



activity of the Fucus sperm and that the optimum temperature 



is probably relatively low. The experiment below is suggestive. 



