Spathidium spathula. 



183 



90 (1672) 



The food reactions of the infusorian Spathidium spathula. 



By LORANDE LOSS WOODRUFF and HOPE SPENCER. 



[From the Osborn Zoological Laboratory, Yale University.] 



Spathidium spathula is an holotrichous infusorian whose sole 

 diet consists of smaller ciliates, chiefly species of Colpidium. If 

 the truncated anterior end of a Spathidium, which is swimming 

 forward and revolving on its long axis, happens to come into direct 

 contact with a Colpidium, the latter usually becomes motionless 

 at once and its protoplasm shows signs of pathological changes. 



Paralysis and death of the prey is apparently brought about 

 by the liberation of a specific substance from the oral region of 

 Spathidium which is toxic to small ciliates. Various authors 

 have ascribed this result to trichocysts about the peristome, but 

 as a matter of fact none are present. However, a number of rod- 

 like bodies can be demonstrated in the thickened rim of the 

 peristome which may represent the seat of the poison. One is at 

 liberty to interpret these bodies as "trichocyst material," though 

 the poisonous nature of trichocysts, even in Paramecium, remains 

 to be demonstrated. 



The paralysis of a Colpidium by a Spathidium results in a marked 

 change in the latter's behavior, which up to this instant has com- 

 prised random swimming movements. If the Colpidium happens 

 to remain against the truncated anterior end, the Spathidium 

 forthwith proceeds by means of the thickened edges of the peri- 

 stome to force its prey down through the slit-like mouth into the 

 interior of the cell. On the other hand, if the Colpidium is not 

 instantly rendered motionless and becomes removed a short dis- 

 tance from the oral region of its captor, the latter institutes a 

 series of rapidly repeated avoiding reactions. This behavior has 

 a tendency to keep the animal in the general vicinity of its quarry 

 because each time the Spathidium starts away its forward progress 

 is checked by the reaction. It is obvious that sooner or later, 

 merely on the basis of chance, the anterior end of the animal will 

 again come in contact with the Colpidium, but a careful study of 

 many captures shows beyond doubt that the apparently random 



