'104 



BEHAVIOR OF THE LOWER ORGANISMS 



FIG. 71. Currents urging 



present author has been unable, after careful study, to detect any differ- 

 ences in the methods of reacting during periods of conjugation. The 

 groups formed on the surface of solids and the rapid movements of the 

 organisms, described by Balbiani (1861, p. 441), as occurring at such 

 periods, are by no means peculiar to conjugat- 

 f / ing infusoria. They take place in the same 

 t* / manner in cultures where none are conjugating. 

 The significant part played in conjugation by 

 the viscidity of the oral surfaces is demon- 

 strated by the peculiar phenomena observed 

 when specimens accidentally come in contact 

 irregularly. This often happens where the ani- 

 mals are numerous. If any part of the body of 

 "one specimen comes by chance against the oral 

 surface of another, the two stick together, with- 

 out regard to their relative position. 



Often groups of three or four or more are 

 two Parameda together when formed in this way (Fig. 70). The individuals 



the oral sides face one another. occupy ^ ^^ Qf irregular pos i t i onSj and e ach 



endeavors to swim forward in his own direction. Some are pulled back- 

 ward, others sidewise, against their vigorous struggles. Often one suc- 

 ceeds in freeing itself, and then swims away ; others remain caught in 

 such groups indefinitely. Even moribund specimens and specimens 

 undergoing fission sometimes thus become united irregularly with 

 others. But the regular union of individuals by the oral surfaces is 

 more common than the formation of irregular groups, owing to the 

 strong tendency, produced by the usual currents, for Paramecia to come 

 together at the oral surfaces. 



During conjugation the two united individuals behave in much 

 the same way as a single specimen. They revolve on the long axis to 

 the left as they swim through the water, and they react to stimuli by the 

 avoiding reaction in the usual way. The direction of turning in the 

 avoiding reaction seems determined usually by one of the components; 

 the pair always turn toward the aboral side of this particular individual. 

 If subjected in the transverse position to an induction shock, only the 

 specimen next the anode responds by ejecting trichocysts (Statkewitsch, 



4. THE DAILY LIFE OF PARAMECIUM 



Let us now try to form a picture of the behavior of Paramecium in 

 its daily life under natural conditions. An individual is swimming 

 freely in a pool, parallel with the surface and some distance below it. 



