REACTIONS OF PROBOSCIS OF PLANARIA 87 



engulf bits of food placed in the mouth." An experiment was performed 

 in which the part of the head in front of the eyes was cut off. Such 

 specimens, from which merely the tip of the head had been removed, 

 reacted normally to food. It is also shown that specimens from 

 which the part of the body posterior to the pharynx has been removed 

 feed like normal worms. - 



We have observed that the reaction of the incomplete pro- 

 boscis of Planaria albissima is variable. When it lacks more 

 than the cell bodies of its basal glands, it shows but little de- 

 parture from normal conduct — the three coordinated move- 

 ments of food ingestion being carried out. 



There is greater variability in the reaction of the proboscis 

 when the sphincter at its base is removed, as the following obser- 

 vations indicate. 



Fig. 1 A, transverse cut removing sphincter of proboscis; proboscis inactive 

 except for ciliary movement. 



A specimen was cut transversely at A, figure 1, so as to free 

 a proboscis which lacked the sphincter. The reaction of the 

 cilia of the external surface of this proboscis carried it from the 

 proboscis sheath. The proboscis then lay for ten minutes by 

 the side of a piece of planarian body and then, without showing 

 any reaction to the food, slowly moved away. There were no 

 opening and closing movements of the mouth on the part of this 

 specimen and there were no peristaltic movements in the wall of 

 the proboscis. In another experiment, after two parts had 

 been removed from the body of the specimen by transverse 

 cutting (fig. 2, B and C), a third cut was made so as to pass 

 through the base of the proboscis (D). Here again the pro- 

 boscis, less a sphincter, swam from the sheath by ciliary activity 

 and then lay quite inactive. Next the proboscis was severed 



2 Quoted from Pearl ('03), p. 523. 



