8 CLASSIFICATION. 



the exception of their miraculous minuteness, to fix upon any 

 character that they possess in common. We are not surprised, 

 therefore, that by the earlier observers with the microscope, they 

 were all grouped together under the very extensive designation 

 of Animalcules, a term simply significative of their small size ; 

 or of Infusorial Animalcules, in allusion to the circumstance 

 that they are generally met with in infusions of animal or of 

 vegetable substances, and are easily attainable by exposing such 

 infusions to the atmosphere. 



Modern improvements in the microscope, and a close attention 

 to the habits and organization of the creatures under considera- 

 tion, have, however, revealed to us the startling fact that in the 

 drop of water under contemplation we have examples of no fewer 

 than three distinct classes of organisms : one belonging to the 

 vegetable, and two to the animal series of creation. By using a 

 very simple test namely, the addition of a little iodine to the 

 drop in which they swim it is found that four specimens in the 

 little group before us, namely, the Volvox (Fig. 2, 2), the Polytoina 

 (Fig. 2, s), the Navicula (Fig. 2, 5), and the Pandorina (Fig. 2, 11), 

 at once turn blue, indicative that they contain starch, a substance 

 thought to be peculiar to the vegetable creation, and thus confess 

 that they are vegetable productions. 



The slimy substance of the Amoeba difflucns (Fig. 2, 6), that we 

 have stated to be continually changing its shape, like the outline 

 of a cloud, refuses to alter its colour under such a test; and. more- 

 over, as it flows or glides from place to place, is seen to devour 

 and to digest the materials with which it is surrounded, thus 

 claiming admission into the animal series, and soon making good 

 that claim by exhibiting attributes and capabilities decidedly 

 of an animal character. The remaining forms (Fig. 2, ], 3, 4, 

 7, 9, 10, 12, 13, M, is), more active and energetic in their move- 

 ments, and evidently of higher capabilities, are all distinguished 

 by having their bodies either partially or entirely covered with a 

 wondrous machinery of vibrating hair-like appendages, which, 

 from their resemblance to our eyelashes, have been named cilia* 

 By the assistance of these admirable organs, the little creatures 

 possessing them are rowed rapidly about from place to place, or 

 causing whirlpools in the surrounding water, drag towards their 

 mouths the tiny victims upon which they feed. The vegetable 

 forms above-mentioned are known to botanists under the names 



* Cilium, an eyelash. 



