164 THE RELATIONS OF PLANTS TO ANIMALS 



of the leaf, and now released into the water by the breaking down 

 of the walls of the cells of the leaves. The bacteria themselves 

 release this food from the hay by causing it to decay. After a 

 few days small one-celled animals appear ; these multiply with 

 wonderful rapidity, so that in some cases the surface of the water 

 seems to be almost white with active one-celled forms of life. If 

 we ask ourselves where these animals come from, we are forced 



Life in the late stage of a hay infusion. B, bacteria, swimming or forming masses 

 of food upon which the one-celled animals, the paramoecia, are feeding; 

 G, gullet; F.V., food vacuole; C.V., contractile vacuole; P, pleurococcus; 

 P.D., pleurococcus dividing. (Drawn from nature by J. W. Teitz.) 



to the conclusion that they must have been in the water, in the 

 air, or on the hay. Hay is dried grass and may have been cut- 

 in a field near a pool containing these creatures. When the 

 pool dried up, the wind may have scattered some of these little 

 organisms in the dried mud or dust. Some may have existed in 

 a dormant state on the hay and the water awakened them to active 



