302 CELL INTELLIGENCE THE CAUSE OF EVOLUTION 



We can see enough of the actions of the cell to demon- 

 strate, I believe, those facts which I claim for him. Take 

 for instance the actions of the single cell called Didinium, 

 which is able to make darts or spears and throw them at 

 its victim from a distance. Its actions are described by 

 Mr. Binet in the following language : "These organs are 

 the weapons used by the Didinium in attacking the live 

 prey which constitutes its sole nourishment. Not only 

 does it attack and devour animalcules almost as large as 

 itself, but frequently it even seizes individuals of its own 

 kind. In such cases it is always Infusoria and never the 

 Rotatoria, although the latter often abound in waters 

 which the Didinium inhabits. It appears, moreover, to 

 have a marked predilection for certain species and so it 

 happens that the huge and inoffensive paramecium aure- 

 lia is almost always its choice by preference among the 

 animalcules that inhabit the same liquid. 



The prehension of food by the didinium exhibits inter- 

 esting aspects which have not as yet been observed in 

 any other Infusory. M. Balbiani in his first observations 

 had often been surprised at seeing animalcules that the 

 didinium had passed by without touching, suddenly stop 

 as if violently paralyzed ; whereupon our carnivorous 

 specimen straightway approached and seized them with 

 seeming facility. More careful examination of the didin- 

 ium's actions soon furnished the key to this enigma. If, 

 while swiftly turning in the water, the didinium happens 

 into the neighborhood of an animalculum; say parame- 

 cium, which it is going to capture, it begins by casting at 

 it a quantity of bacillary corpuscles, which constitutes its 

 pharyngeal armature. The paramecium immediately 

 stops swimming and shows no other sign of vitality than 

 feebly to beat the water with its vibratile cilia ; on every 

 side of it, the darts lie scattered that were used to strike 



