CLASSIFICATION AND CEEATION. 53 



one would hardly suspect that they were endowed 

 with life. To the superficial observer they all 

 look alike, and it is not strange, that, before they 

 had been more carefully investigated, they should 

 have been associated together as the lowest divis- 

 ion of the Animal Kingdom, representing, as it 

 were, a border-land between animal and vegeta- 

 ble life. But since the modern improvements in 

 the microscope, Ehrenberg, the great master in 

 microscopic investigation, has shown that many 

 of these little globules have an extraordinary 

 complication of structure. Subsequent investi- 

 gations have proved that they include a great 

 variety of beings : some of them belonging to the 

 type of Mollusks ; others to the type of Articu- 

 lates, being in fact little shrimps ; while many 

 others are the locomotive germs of plants, and so 

 far from forming a class by themselves, as a dis- 

 tinct group in the Animal Kingdom, they seem 

 to comprise not only representatives of all types, 

 except Vertebrates, but to belong also in part to 

 the Vegetable Kingdom. 



Siebold, Leuckart, and other modern zoolo- 

 gists, have considered them as a primary type, 

 and called them Protozoa ; but this is as great a 

 mistake as the other. The rotatory motion in 

 them all is produced by an apparatus that exists 

 not only in all animals, but in plants also, and is 

 a most important agent in sustaining the fresh- 



