BEHAVIOR 27 



To these frequent reactions may be added the "decision" to 

 encyst or excyst, as well as the special response to each other 

 which leads to the joining of pairs in a specific orientation for 

 sexual conjugation. Of special interest is the accommodation to 

 repeated adverse stimuli which Jennings demonstrated and which 

 may be regarded as the best evidence of a primitive type of 

 learning in unicellular organisms. 



The ease with which stentors lend themselves to micrurgical 

 operations should provide opportunities for analyzing the struc- 

 tural basis of coordination. After the immediate contraction 

 response to cutting, stentors show no evidence of '' pain " or 

 lingering effects of injury as the fragments or cut animals swim 

 away in a remarkably normal manner. Later they mend the cut or 

 regenerate missing parts, but between the time of cutting and 

 repair or reconstruction there is, it would seem, a sufficient period 

 for observing effects on behavior of specific lesions and ablations. 

 Are there circumferential cuts at certain levels of the cell axis 

 which abolish coordination between adjacent rows of body cilia so 

 that spiral swimming is prevented, or may such cuts prevent attach- 

 ment or detachment of the holdfast? Are stentors from which the 

 oral pouch has been removed or those — after a method which 

 will be described later (p. 172) — developing without a pouch still 

 capable of food selection? If not, could they be made to ingest 

 unusual materials relevant to analysis of their metabolism? If 

 decapitation abolishes the avoiding response to light in coeruleuSy 

 can selective ablations at the anterior pole demonstrate the sensitive 

 area ; and do similar operations also prevent the positive response to 

 light in niger? Do stentors temporarily bereft of ingestive organelles 

 still show the avidity of normal animals evidenced by quicker 

 accommodation to mechanical stimuli when in the presence of 

 food after a period of deprivation, or is the successful formation of 

 food vacuoles the necessary prelude to this behavior? 



These questions are but a sample of possible ways in which 

 behavior on the cell level might be- investigated in a form so 

 amenable to operation as Stentor. Might the neurone itself, then 

 be capable of considerably more " behavior " than mere 

 ''excitation", realizing as part of the nervous system something 

 of the potentialities which have been evolved in a different manner 

 but from the same cellular origins, in ciHates? 



