Descriptive Biology 



93 



of the green plant. Yet others contain within themselves the 

 magic chlorophyl, whose beautiful green delights our eyes in 

 the early verdure of the spring, and by whose means Nature 

 performs her wonderful chemistry, converting carbon dioxide 

 and water into sugar, which plants and animals alike, may 

 use as food. Many, notably the Sporozoa and some flagel- 

 lates, are parasitic, and in some cases are the cause of plagues 

 of man and beast. 



In the world of the little as well as in that of the great, 



V 



LOWER PLANT LIFE 

 1, Spirogyra; 2, desmids; 3, a diatom. 



1 and 3 original, 3 from a preparation by Elmore, 2 from Needham & 

 Lloyd's "Life of Inland Waters, " Comstock Publishing Company. 



we find the role of the hunter and the hunted. Usually it is 

 the smaller fry which are the victims, but sometimes it is they 

 which take the hunter's part, attacking and destroying animals 

 much larger than themselves. Chief among these is Didin- 

 ium, a little creature about 1/150 inch in length with a bor- 

 ing proboscis by means of which it attacks and engulfs other 

 Protozoa from three to six times as large as itself. The cus- 

 tomary daily ration of this little gourmand is one or two 

 Paramo3cia, but when especially hungry it may consume as 

 many as four or five of these animals. 



As protection against their insatiable foes many Protozoa 



