THE BEHAVIOR OF INFUSORIA; PARAMECIUM 



103 



Each tries to continue its course, so that they pull in opposite directions. 

 One may drag the other along with it, or the two may finally pull apart. 

 There is of course a tendency for objects to be brought against the 

 oral groove, owing to the strong current of water that passes along this 

 region ; it is through this fact that Paramecium gets its food (compare 

 Fig. 46). This tendency operates on other Paramecia in the neigh- 

 borhood as well as on inanimate objects. If two Paramecia are close 

 together with oral grooves facing each other (Fig. 71), this tendency is 

 reciprocal; each tends to draw the other to its own oral surface. On 



Fig. 70. — Groups of individuals adhering to each other by their oral surfaces, from cultures 

 of Paramecia undergoing conjugation, a. Two attached individuals swimming in opposite 

 directions, b, Three individuals attached by their oral surfaces to a fourth, c. Three indi- 

 viduals irregularly attached, d, A conjugating pair, swimming to the left, with a third individual 

 attached by its oral surface to the posterior part of one of these, and a fourth individual trans- 

 versely attached to the third. The third and fourth were dragged about by the first pair. 



the other hand, if the aboral surfaces face each other, the currents tend 

 to separate the two Paramecia. Hence when two Paramecia come in 

 contact it will usually be by the oral surfaces. This often happens under 

 usual conditions, but no conjugation results, because the oral surfaces 

 have no tendency to adhere ; the animals therefore quickly separate 

 again. But at times when the oral surfaces are viscid, specimens which 

 come thus in contact remain united. The succeeding internal processes 

 fall in the field of physiology rather than that of behavior. Details 

 concerning them will be found in text-books of zoology. 



Thus nothing seems to be required for producing conjugation be- 

 yond the usual movements and the viscidity of the oral region. The 



