NEGATIVE PHOTOTAXIS ETC. OF Littori na. 



5 



Thus the half of the plate tamed toward the land which appeared 

 naturally darker on account of bushes, grasses etc, had nearly three 

 times as many individuals as the half turned toward the sea. When it 

 is recollected that the sun was at the time shining from the zenith, the 

 reaction must be considered as very decided. It was evident that 

 whether these molluscs have other means or not, the property of 

 negative phototaxis alone must induce them to crawl landward and 

 to make them behave as if they knew the differences between the land 

 and the sea. 



There was another series of experiments which I shall detail next. 



Experiment 7 (Aug. 7) 

 on each side (Fig. 4), two 

 glass-plates A and B* were 

 placed, forming an in- 

 clined plane as shown in 

 the annexed woodcut of 

 the side-view. A third 

 glass-plate C was put on 

 the upper edges of the 

 aquarium against the in- 

 clined plane so as stop 

 any mollusc that may 

 come up the incline. The 

 whole was placed so that 

 light was falling on the 

 inclined plane in the direc- 

 tion of the arrow in the 

 lower figure. 



A large number of shells was placed at the spot / on the bottom of 



* There was no reason why two plates should be used instead of one. This was 

 rather a drawback than otherwise. Moreover one of the plates, B. was not a whole one. 

 Only these were the best arrangement I could make at the time. I must apologize for 

 the crudity of arrangements in my experiments. 



