CHAPTER I. 



APPLICATION OF THE FOREGOING PRINCIPLES TO THE 

 LOWEST ANIMALS. 



Protozoa. 



No one can have watched the movements of certain 

 Infusoria without feeling it difficult to believe that these 

 little animals are not actuated by some amount of intelli- 

 gence. Even if the manner in which they avoid collisions 

 be attributed entirely to repulsions set up in the currents 

 which by their movements they create, any such mechanical 

 explanation certainly cannot apply to the small creatures 

 seeking one another for the purposes of prey, reproduction, 

 or, as it sometimes seems, of mere sport. There is a 

 common and well-known rotifer whose body is of a cup 

 shape, provided with a very active tail, which is armed at 

 its extremity with strong forceps. I have seen a small 

 specimen of this rotifer seize a much larger one with its 

 forceps, and attach itself by this means to the side of the 

 cup. The large rotifer at once became very active, and 

 swinging about with its burden until it came to a piece of 

 weed, it took firm hold of the weed with its own forceps, 

 and began the most extraordinary series of movements, 

 which were obviously directed towards ridding itself of the 

 encumbrance. It dashed from side to side in all directions 

 with a vigour and suddenness which were highly astonish- 

 ing, so that it seemed as if the animalcule would either 

 break its forceps or wrench its tail from its body. No 

 movements could possibly be better suited to jerk off the 

 offending object, for the energy with which the jerks were 

 given, now in one direction and now in another, were, as I 

 have said, most surprising. But not less surprising was 



