FRANDSEN. — REACTIONS OV LIMAX MAXIMUS. 



217 



TABLE XI. 

 Responses of Individuals to Different Intensities of Light. 



In all these cases, there if seen to be a gradual diminution in the degree 

 of response as the intensity of light diminishes. Again, from an animal 

 which responded negatively to a certain intensity of light, a positive 

 response could be got by weakening the light sufficiently (Nos. 2 and 3, 

 Table XII.), and a positive animal could be made to give a negative 

 response by using stronger light (No. 1, Table XII.), as the following 

 instances show. 



TABLE XII. 

 Responses of Individuals to Different Intensities of Light. 



No. 3, Table XII., shows a less regular response than any of the other 

 animals. From a response of — 37° it drops to one of — 2.5°, and, under 

 the influence of a still lower intensity of light, it again rises to a marked 

 negative response of —32.° At a still lower intensity, it gives a striking 

 positive response of +36°. Here, however, we have well illustrated in 

 particular individuals the law laid down for all slugs, — that they are 

 negatively phototaetic to strong intensities of light, the precision of re- 

 sponse varying correlatively with the intensity of the stimulus ; that to 

 weak intensities they are positive ; and that to a certain intermediate 

 intensity they are neutral. 



A glance at the intensity column (Table X.) shows that the slugs are 



