4 FIRST LESSONS IN ZOOLOGY. 



like a fish or dog. Such animals as these differ from lilies 

 or trees in being able to move about, in having a stomach, 

 heart, eyes, ears, a nose, nerves and muscles. But when we 

 place under the microscope the red-snow or a similar plant 

 (Fig. 2) and compare it with a monad (Fig. 3), which is one 

 of the lowest animals, it is difficult to tell which is vegeta- 

 ble and which animal. Both are formed of protoplasm, 

 both move about by little thread-like appendages, and both 



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FIG. 4. Forms of Bacteria, or disease-germs. (Highly magnified.) 



multiply in the same manner. The slime-moulds, and even 

 the disease-germs (Fig. 4), are by some authors regarded 

 as animals. 



It is only by a study of the connecting links between 

 these lowest beings, leading up to what are undoubted 

 animals or plants, that we are enabled to refer them to 

 their proper kingdom. 



As a rule, plants have no special organs of digestion or 



