THE BEHAVIOR OF PROTOZOA 79 



which many specimens gather at times. Of course they get 

 no food in this way." They make attempts on various other 

 organisms with which they come into contact, but often 

 fail on account of the toughness or large size of the organism 

 attacked. 



What seems at first to be choice of prey is really some- 

 thing quite different. The infusorian swallows what it 

 can and not what it will. "The apparent choice of food/' 

 says Mast, "is due to the fact that the seizing organ will 

 adhere to some organisms and not to others. The Didinia 

 come in contact with all sorts of objects in their random 

 swimming and attempt to swallow all those to which the 

 seizing organ will adhere." After all Didinium like Para- 

 moecium is a pretty simple sort of a creature in its be- 

 havior. It has but a few simple tricks which it tries 

 over and over again. Its going gunning with its armory 

 of projectiles, its accurate sense of position and its marks- 

 manship are all creations of the observer's fancy. 



A protozoan exhibiting somewhat more complex behavior 

 than is shown by Paramoecium is the large ciliate Loxophyl- 

 lum meleagris. This organism usually glides along the 

 surface of objects by means of cilia on the side of the body, 

 but at times it may swim in a spiral manner through the 

 water. If strongly stimulated while swimming it may 

 back off and turn in another direction much as Paramoecium 

 does, but the organism seems to be averse to swimming and 

 generally takes advantage of the first opportunity to glide 

 along over some solid object or the surface film. These 

 gliding movements are carried on in a more or less rythmical 

 way most of the time. The body is narrowed and elongated 

 and swims forward for a short distance, then there is a con- 

 traction resulting in making the body shorter and broader 

 and at the same time a reversal of the effective beat of the 



