REACTIONS OF PROBOSCIS OF PL,ANARIA 99 



the more anterior portions of the central nervous system may 

 result in slight disturbance of the proboscis, -while the gangha 

 adjacent and anterior to the base of the proboscis ordinarily act 

 as inhibitors to the ingesting reflexes of the proboscis. 



REACTION TO FOOD OF FREED PROBOSCIS 



The ability of the proboscis that had undergone autoampu- 

 tation to distinguish between food and non-food was tested in 

 the following manner: After a proboscis had separated from the 

 body it was washed in several changes of fresh tap-water to 

 free it from any solutions or particles of its own body, than 

 might serve as a stimulating agency to the proboscis. Frag- 

 ments of washed cover-glass were placed into clean water that 

 contained such a washed proboscis. In some instances these 

 fragments of glass were accepted by the proboscis and were passed 

 by the sphincter and thrown from the organ as food is handled 

 by free proboscides. The ingesting of objects by a freed pro- 

 boscis displays no choice, hence it is a reflex. 



CONCLUSIONS 



1. All proboscides of Planaria albissima that have been sev- 

 ered from their adjacent ganglia show some reaction by dis- 

 turbed movements within the proboscis-sheath. Most of the 

 proboscides thus separated from the central nervous system 

 underwent autoamputation while lying within the sheath. In a 

 relatively few instances we have found that, unless the pro- 

 boscides in addition to being cut off from the central nervous 

 system have been excited by a disturbing of the thigmotactic 

 conditions within the sheaths, they do not undergo autoamputa- 

 tion. In all cases, however, the disturbance of the thigmotactic 

 conditions of the sheath so excites the proboscis that, without the in- 

 hibitory control of the adjacent ganglia of the central nervous sys- 

 tem, the proboscis suffers autoamputation and acts as an independent 

 reflex organism. 



2. The freed proboscis is able to carry out the three co- 

 ordinated muscular movements involved in the mechanics of 



