io6 



Herbert Eugene Walter 



Fig. 10. Dendrocoelum, i8 min. 



Fig. II. Phagocata, 60 min. (still moving). 



Fig. 12. Bdelloura, 15 min. 



Fig. 13. Planaria maculata, 47 min. 



Fig. 14. Planaria gonocephala, 60 min. (still moving). 



Woodworth ('97) in contrasting the activity of Planaria macu- 

 lata, P. gonocephala and P. dorotocephala states that individuals 

 of the latter species remain in motion longer than individuals of 

 the other two — an observation confirmed by Pearl ('03). 



Degree of Wandering. If a worm is started at the center of a 

 circle parallel to the direction of the light and pointing away from 

 its source, then the more devious its course the more it may be said to 

 wander. Both generic and specific differences were obtained bear- 

 ing upon this phase of behavior. Selected instances of such dif- 

 ferences are given in Table XX, expressed in average degrees of 

 deviation upon emergence from a circle 10 cm. in diameter. 



TABLE XX 



The average generic and specif c di'^erences between individuals of four genera and two species of 

 planarians expressed in degrees of deviation upon leaving a circle 10 cm. in diam. In every 

 instance the worm was started away from the source of the light 



The remarkably large deviation shown by Bdelloura is due to the 

 fact that it is a positive worm. When pointed toward the light 

 its deviation was only 39-3°, a number which would perhaps be 

 more justly comparable with the other records in this table. But 

 even so, it will be seen that Bdelloura, of all the forms observed, 

 is the least oriented by directive light. Specific differences in 

 the degree of wandering are in general less marked than the 

 generic differences, according to the records in Table XX. 



