RHYTHMICAL ACTIVITY IN INFUSORIA. 



S. J. HOLMES. 



While much in the behavior of the infusoria comes under the 

 head of direct responses to external stimuli, there is, in many- 

 forms, an extraordinary amount of activity which cannot be traced 

 to any outside cause. In addition to those forms which keep up 

 a continuous swimming with never-flagging energy, there are 

 several infusorians which perform movements of a more or less 

 regular rhythm. These are analogous to such rhythmical move- 

 ments as the beating of the heart of higher animals, or the 

 rhythmical pulsations of the swimming of a jelly-fish. They are 

 more automatic than the latter, and are, perhaps, more closely 

 comparable to the regular pulsations, which, under certain con- 

 ditions, are performed by some species of jelly-fish after removal 

 of the nerve ring and marginal sense organs. 



More or less regular and apparently spontaneous movements 

 have been noted in a few species (Stentor, Vorticelld) by various 

 writers, but the subject has received scarcely more than a passing 

 mention. My attention was called to this feature of the behavior 

 of certain infusoria in some studies recently made on the behavior 

 of Loxophyllum meleagris, and I was led to look for similar 

 phenomena in other forms. Observations were made on the fol- 

 lowing species : 



Loxophyllum meleagris. — Loxophyllum commonly moves 

 about on some solid object by extending the body, gliding for- 

 ward a short distance, then swimming backward, turning toward 

 the oral side and then going forward again. The changes in the 

 direction of movement are not due to any obstacles encountered ; 

 they occur in much the same way when there are no objects in 

 its course. The organism frequently keeps up this kind of move- 

 ment for a long time in very nearly the same locality. The body 

 is always narrowed in swimming forward, and always widened 

 in swimming backward, thus showing a constant correlation of 

 the contractile activities with the direction of the ciliary beat. If 

 the body is cut in two, the pieces will undergo the same rhyth- 



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