Prof. Ehrenberg's Researches on the Infusoria. 203 



common all animals possessed of a certain degree of minuteness, 

 without any further inquiry. For this term has been substi- 

 tuted the successive appellations of Animalculi, Animalia Mi- 

 croscopica, Phytozoa. But as there is none which is not liable to 

 some objection, perhaps it will be as well to retain the original 

 one conferred on these animals by the Danish naturalist Mialler, 

 than whom none has a better title to the honour of conferring it. 



I fancy my reader to pause at the mention of structure and 

 functions in animals, the discovery of whose existence merely 

 has been hitherto deemed the ultimatum of zoological research, 

 and regarding whom the sum-total of our knowledge has been 

 hitherto confined to a few details on their external forms and 

 active motions. Yet, in the midst of their transparent tissues, 

 the German naturalist has, by a peculiarly ingenious method of 

 observation, developed a highly complicated organization, which, 

 with those who arrange the animal kingdom in a linear series, 

 will remove them far from the extremity of the scale. The ex- 

 istence of a digestive, muscular, and generative apparatus, is es- 

 tablished beyond a doubt ; and organs have been also discover- 

 ed which, bear great analogy with the vascular and nervous sys- 

 tems. The great changes v/hich these facts must make in the 

 systematic distribution of these animals, are obvious. Nay, from 

 some circumstances, we are inclined to believe, that future ob- 

 servations may place these microscopic creations in a parallel 

 order with their more apparent prototypes, and with not less 

 varied and interesting gradations of structure. 



Leaving, however, these speculative ideas, let us proceed at 

 once to a brief exposition of the leading facts demonstrated by 

 Dr Ehrenberg. But it will be necessary, to the full understand- 

 ing of the value of his discoveries, to give a short historical sum- 

 mary of the systems and observations which existed previously 

 on infusory animals. We shall, therefore, class our observations 

 under the four following heads. 1. History of Phytozoology. 

 2. Organization of Infusory Animals. 3. Their Classification. 

 4. Their Geographical Distribution. 



I. History of Phytozoology. 

 Previous to the time of Miillcr, observers seem to have had 



o2 



