WHAT KINDS OF THINGS ARE LIVING? 19 



Returning for a moment to feeling, we can easily convince 

 ourselves that there is more to the antennae than a mere wild 

 waving. There is about the animal something that makes it 

 move under certain outward conditions which act upon these 

 feelers. Moreover, there is something about the animal that 

 makes it move under certain conditions which act upon the eyes. 



Without looking into the interior of the animal we can learn 

 that it takes food and grows, that it feels or sees and moves, 

 and that it reproduces. And so much we can say of all the 

 animals we know. Some eat one kind of food, some another ; 

 some grow rapidly, some slowly ; but all take in food and grow. 

 So, too, animals differ as to how sensitive they are, as to what 

 kinds of conditions influence them, and as to how rapidly or 

 how vigorously they move ; but all are sensitive to changes and 

 all do move. And all animals originate from other animals ; 

 that is, all species of animals reproduce themselves. 



15. Activities of plants. What now of our plant? Does it 

 also move ? Is it sensitive to what goes on around it ? We know 

 •very well that plants grow, and everybody who has ever thought 

 of getting new plants for any purpose knows that they com- 

 monly come from seeds, and that these seeds in turn come from 

 other plants. Plants, then, do reproduce themselves. But if 

 plants really do move, and if they really do respond to changes 

 in their surroundings, most of us have not noticed these facts. 

 Still, the very fact of taking in food, which is essential to growth, 

 implies some movement. To be sure, plants do not reach out 

 and grasp food, as do the grasshopper and the baby, for ex- 

 ample ; nor does the plant eat with a mouth ; yet it does take 

 materials into itself from the surroundings (by way of the roots 

 and by way of the leaves), and it transports, or moves, these 

 materials from one part to another. 



Most of the movements in a plant are slow and minute, so 

 that we should need a microscope to observe them directly. 

 But the rapid movement of the leaves in a disturbed sensitive 

 plant, and the slower but very distinct turnings of many com- 

 mon plants under one-sided illumination, are easily observed. 



