n6 



Herbert Eugene Walter 



If the relationship of an animal could be determined by behav- 

 ior alone, there need be no hesitancy in saying that this unidenti- 

 fied planarian should not be classified under the species Dendro- 

 ccelum lacteum, since in all the criteria mentioned in the foregoing 

 table it stands at an opposite extreme to Dendrocoelum. In 

 point of fact its behavior more closely resembled that of Phago- 

 cata gracilis, a species which, according to Dr. A. M. Banta, who 

 kindly furnished the cave planarian for this study, is common in 

 the streams in the vicinity of the cave where the latter was found. 



table xxx 



The behavior of a cave planarian compared with that of planarians accustomed to light. 





The cave 

 planarian 



Other planarians 



Criteria of behavior 

















Number 



Average 



Average 



Maxi- 



Mini- 



Range 





of trials 



record 



record 



mum 



mum 



Average amount of negativeness, expressed 















in the percentage of deviation upon leav- 















ing a circle 10 cm. in diameter when 















started at right angles to incident light 



70 



99.6 



91.8 

 (B 



99-9 



delloura 



84.6 

 omitted) 



15-3 





60 





1.203 



1-473 



0.853 





Average seconds required to leave a circle, 











90 



27.8 



52.2 



62.2 



39-7 



22.5 



Average deviation in degrees when pointed 





away from the light. (Amount of wan- 

















46 



47° 



25°.6 



39°-3 



9°-4 



2 9 °. 9 





Summary. Average individual behavior constitutes typical 

 specific behavior. Variations in individual behavior make accu- 

 rate predictions of responses to stimuli under given conditions, 

 impossible. The rate of locomotion of the same individuals varies 

 from day to day even under apparently identical conditions. 

 Individual variations in the rate of locomotion, in the range 

 between maximum and minimum rates, and in the percentage of 

 clockwise turnings, are more variable than the average behavior 

 in these particulars under different light intensities. 



An unidentified cave planarian showed greater activity and 

 more inclination to wander than any of the other planarians under 

 observation. 



{To be continued) 



