480 Journal of Comparative Neurology and Psychology. 



the spiral path coincident with the direction of the force in 

 question. Under the action of the three agents named, as a 

 rule it is the minus change that induces reaction ; hence the 

 animal directs itself against the operation of the forces at work. 



B. BcJiavior during Conjugation. 



The behavior during conjugation is not brought about 

 through the avoiding reaction, yet the conditions determining 

 it seem of the same character as those determing behavior pro- 

 duced through the reaction named, so that it should be consid- 

 ered in relation with the latter. It is not my purpose to 

 give here a full account of the behavior during conjugation, but 

 merely to point out the part played in this behavior by the 

 usual "action system" of Paramecium, above set forth. 



Paramecia during a period of conjugation are perhaps in 

 a "physiological state" differing from the usual state, so that 

 they react differently from usual, uniting in pairs. Yet it is re- 

 markable how much of their behavior at such times is due to 

 precisely the same features that are always present, taken in 

 connection with a physical modification of the body substance. 

 I have not thus far been able to observe at such times any 

 method of reaction differing from the usual ones. The factors 

 bringing together two individuals seem to be chiefly the follow- 

 ing. 



I. At these periods of conjugation the oral surface of Para- 

 mecium is adhesive, through some physical modification of the 

 protoplasm. As a result of this modification other Paramecia 

 coming in contact with the oral surface become attached. The 

 position of the two Paramecia is of no consequence, nor the 

 way in which the contact is brought about, provided only that 

 one animal comes in contact with some part of the oral surface 

 of another. As a result of this fact, the individuals in a crowded 

 culture become stuck together in all sorts ot bizarre ways, and 

 evidently' without any previous definite reaction on the part of 

 the individuals concerned. Two specimens will be seen feed- 

 ing on the bacterial zoogloea and moving in opposite directions 

 over its surface ; one crosses by ciiance the path of the other, 



