MOVEMENTS, ETC., OF FRESH-WATFE PLANARIANS. 669 



unfed, but this was ueitlier marked nor of general occur- 

 rence. This experiment was afterwards repeated with other 

 specimens, and witli sugar as the stimuhis, with essentially 

 the same results. I have also repeatedly tried stimulating 

 with various solutions specimens which had just ceased 

 feeding, and in these cases found no certain difference 

 between their behaviour and that of specimens which had 

 not been fed for some time, with regard to the giving of the 

 positive reaction. It would appear, then, that so far as the 

 giving of the positive response to weak stimuli is concerned, the 

 amount of food the animal has previously had is of very little 

 cousequence. The failure of fully fed specimens to give the 

 full feeding reaction on the end of the capillary tube indicates 

 that the physiological changes induced by recent feeding 

 affect the performance of the food-taking rather than the 

 food-seeking reflexes. 



3. Un localised Action of Chemicals. — An extensive 



Fig. 35. — Diagram showing llieform of crawling movement, exliibited 

 by Planaria wiien placed in 10 per cent. NaCl. 



series of experiments on the effects of immersing planarians 

 in various solutions was performed, but as the results threw 

 but comparatively little light on the general nature of the 

 behaviour, they will be reported only briefly. Immersion in 

 any strong solution causes marked changes in the move- 

 ments. The gliding is made very much slower or entirely 

 disappears. In 10 per cent. NaCl a peculiar form of crawling 

 appears. Very pronounced contraction waves pass over the 

 body longitudinally, giving it the appearance shown iu 

 Fig. 35. In 2 per cent. CuSO.i the animals make no pro- 

 gressive movements, but wave the head violently from side to 

 side. In strong solutions of acids the worms squirm violently 

 without making any effective progressive movements. In all 

 these strong solutions the sensitiveness to all stimuli is 



VOL. 46, PART 4. NEW SKRIES. X X 



