OBSERVATIONS ON CILIARY CURRENT IN FREE- 

 SWLMMING PARAMECIA 



S. O. .MAST AND K. S. LASHLEY 

 From the Zoological Laboratory of the Johns Hopkins University 



SIX FIGURES 



INTRODUCTION 



When paramecia are at rest and are feeding, a cone-shaped 

 current from a considerable distance in front of the animals pro- 

 ceeds down the oral groove toward the mouth. This current 

 may be called a feeding-cone or merely a cone. Similar currents 

 are sometimes seen when the animals approach a region contain- 

 ing particles of carmine or India ink. WTien this occurs the 

 particles in suspension are drawn toward the paramecia from in 

 front in such a way that they appear to come in contact with the 

 oral groove before the anterior end reaches the original boundary 

 of the region. Jennings demonstrated this very clearly ('06, p. 

 45). He maintains that this phenomenon occurs not only when 

 the paramecia approach a foreign substance but that it occurs 

 continuously in free-swimming animals, and that it serves them 

 in detecting in advance the condition of the environment they 

 are about to enter, thus making it possible to avoid injurious 

 substances and unwholesome regions, without actually getting 

 into them. He says ('06, p. 47), 



Paramecium is continually receiving 'samples' of the water in front 

 of it. Since in its spiral course the organism is successively pointed 

 in many different directions, the samples of water it receives likewise 

 come successively from many directions (fig. 33).^ Thus the animal is 



' This figure represents a Paramecium proceeding on a spiral course, and 

 continuously drawing in from some distance in front, a cone-shaped current. 

 It has been extensively copied, especially in general zoological works. If our 

 conclusions are correct the shaded regions representing currents in this figure 

 should be omitted. 



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