60 LOCOMOTION OF POLYCLADS 



alone. Miss Stringer ('17) has made this same criticism of the 

 accepted view of the means of locomotion in the triclad planarians 

 and Crozier ('18) claims that in the Leptoplana 'tincta' "when 

 muscular waves are absent, no creeping progression can be de- 

 tected." Pieces of any size and from any portion of the body 

 of the Monterey polyclads show this same ciliary movement in 

 chloretone. This ciliary action is therefore not dependent on 

 the central nervous system. 



The slow creeping movement is accomplished by means of the 

 constant slight muscular contractions to which Child ('04) refers. 

 There are no definite waves, but the entire ventral surface appears 

 to be thrown into irregular ripples. This can be especially well 

 observed when the polyclad is creeping under the surface film of 

 the water. E. cavicola is especially favorable for observation, 

 since the animal is a broad oval, some 3 cm. in length by 2 in 

 width. The animal lays down a track of mucus as it proceeds. 

 The midventral region is depressed and fairly quiet, as if this 

 portion were holding on by suction, while the margins are espe- 

 cially active. The rippling motion is due to momentary local 

 release of a portion of the ventral surface from its point of at- 

 tachment and a shifting of this area by muscular contraction. 

 These worms are able to go both forwards and backwards and to 

 turn to one side. The movement is slow and often irregular. 

 Pieces formed by longitudinal cuts always moved in circles to- 

 ward the injured side (cf. Child). With P. calif ornica and E. 

 cavicola the rate of progress averaged some 0.5 mm. per second. 

 The other species moved slightly faster, but so seldom in a straight 

 line that accurate measurements were not obtained. Worms with 

 the cephalic ganglia removed and pieces from any region anterior 

 or posterior to the brain exhibited this ataxic (Olmsted, '17) type 

 of locomotion. The rippling muscular movement persisted for 

 some fifteen minutes in a saturated solution of chloretone in sea- 

 water, but finally ceased if the animal were undisturbed. The 

 slow creeping movement is therefore under control of that part 

 of the nervous system in the immediate locality of each muscular 

 contraction and is a local phenomenon. 



