MOVRMENTS, ETC., OP FRKSH-WATKR TLANARIANS. 539 



obtained by an objective study of the phenomena : precisely 

 what these imply as to internal factors would doubtless be a 

 subject of dispute among psychologists of different schools. 



E. Normal Motor Activities. 



Under this heading will be included all the purely motor 

 phenomena of the organism. This will include the 

 movements (without refei-ence to special reaction to stimuli), 

 the coming to rest^ and the general resting condition of the 

 organism. 



The movements natui*ally fall into two categories; (a) 

 locomotor movements, and [h) non-locomotor, including such 

 movements as contractions and expansions and the like. 



I. Locomotor Movements. 



As has been mentioned above (p. 19), thei-e are two sorts 

 of locomotor movements, the gliding and the crawling. The 

 gliding is the smooth, even motion by which the flat-worm 

 slips about over surfaces Avithout showing a perceptible 

 ripple of muscular movement. This is the characteristic 

 movement when the organism is not particularly stirred up. 

 The crawling is the characteristic movement when the animal 

 is, or has been recentl}', strongly stimulated. It is a purely 

 muscular movement. 



a. Gliding. — The movement which I have called gliding 

 is apparentl}'' the same as that which has been called " swim- 

 ming " by Bardeen (loc. cit., p. 15), yet it must be stated that 

 in all of my observations on a very large number of plana- 

 rians I have never seen anything corresponding to some of 

 the details which this author mentions in this movement. 

 In the first place, he speaks of the worms moving progres- 

 sively when not in contact with a solid body, i. e. of a 

 movement freely through the water. This I am unable to 

 understand, as I have never seen the slightest indication of 

 the organism moving freel}'^ in the water without contact 

 with a solid body or something which served the purpose of 



