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CHARLES HARLAN ABBOTT 



taxis is altered by throwing the animals into water. The effect 

 is due, according to Holmes' explanation, to unusual contact 

 stimuli. 



6. Comparison of phototaxis in Oniscus and Porcellio 



In the foregoing discussion many references have been made 

 to differences between Oniscus and Porcellio. Any conclusions 

 which may be drawn from these experiments in modifiability of 

 behavior will be more clear after consideration of this generic 

 difference. 



A comparative study of the phototaxis of Oniscus and of 

 Porcellio is given in table 10, which records the angles of nega- 

 tiveness in six series of experiments, most of them already 

 reported in the preceding pages. 



TABLE 10 



Comparison of angles of negativeness of Oniscus and Porcellio in various photo- 

 taxis experiments. A, animal facing light; B, animal facing aivay from light; 

 C, right side illuminated; D, left side illuminated 



As the parallel columns show little differences in the two 

 methods of compiling results, the angles from positions C and D 

 will be referred to, whenever, in the discussion, quotations are 

 made from the table. 



1. The phototactic response of Oniscus was negative, with 

 little variation in the degree of negativeness under the different 

 conditions. The averages, from the lowest (117°) to the highest 

 (135°), show a range of only 18°, which is less than the difference 



