The Reactions of Planarians to Light 



III 



specific behavior would include more phases of action than indi- 

 vidual behavior. 



In the present series of records hardly enough representatives 

 of different genera and different species were under consideration 

 to establish any convincing generalization on this point. 



table xxv 



Comparisons in behavior, generic and specific 







Generic differences 





Specific 



differences 



Criterion of behavior' 



Dendro- 

 ccelum 



Phagocata 



Planaria 



Bdelloura 



Planaria 

 maculata 



Planaria 



gono- 



cephala 



(i) Percentage of negativeness 



93- 1 



89.6 



92.2 



11 



99-9 



84.6 



(2) Character of course in di- 















rective light 















\ 



without 



with great 



with 



with 







Turns toward the light < 



much 



indiffer- 



much 



ease 



No 



contrast 



I 



difficulty 



ence 



difficulty 







" ■ 





plainly 



slightly 



slightly 



none 



slightly 



slightly 



Wigwag movements . . . 



few 



few 



few 



many 



few 



few 



(3) Average duration of move- 















ment 



18 min 

 9-4 



60+ min. 

 3°- 



? 

 24.6 



15 min. 

 39-3 



47 min. 

 21.6 



60+ min. 



(4) Amount of wandering. . . . 



27.7 



(Av. deviation in degrees) 

















0.85 



I--39S 



1.270 



? 



1.470 



i-°75 



(In mm. per sec.) 















(6) Seconds required to leave 















a 10 cm. circle 



62 



40 



54- 



? 



47 



60 



(7) Comparative influence of 









fatigue, per cent 



22 



0.25 



12.4 



? 



18 



6.8 



(8) Percentage of response to 















change in light intensity. 



17 



37 



5 2 -5 



? 



55 



5° 



(9) Manner of coming to rest. 



in dark 

 in exclu- 

 sive groups 



in dark 



in dark 



in light 

 in rosettes 



in dark 



in dark 



B Individual Behavior 



The analysis of specific behavior leads to the study of individ- 

 uals, since it is the average activity of different individuals that 

 makes up the behavior typical of the species. In biological litera- 



