CLASS II. INFUSORIA. 



OF this very extensive group of living beings a 

 large number are marine ; and the slightest exam- 

 ination, with a pocket lens, of sea- water that has 

 been kept for a little while in an aquarium, proves 

 that these creatures exist in considerable variety 

 in our own seas. But no naturalist, that I am 

 aware of, has as yet attempted the great work of 

 identifying and discriminating the British Infusoria ; 

 and the only help to the student that exists for 

 this object is the magnificent " Die Infusions- 

 Thierchen" of Professor Ehrenberg, or Mr. 

 Pritchard's abridged translation of it, " A History 

 of Infusoria, living and fossil." 



But since the publication of that great work, 

 important alterations have been made in the limits 

 of the class ; and the whole group, as a legitimate 

 division of the Animal Kingdom, is in abeyance. 

 Whole genera have been shown to be only the 

 young stages of higher animals, as Bursaria, Para- 

 mecium, &c., which are the larvae of certain Plana- 

 rice, and others have proved to be vegetables, endued 

 with spontaneous motion. Hence, though I do 

 not go so far as those who believe that the whole 

 group will ultimately be resolved into other classes, 

 I agree with Dr. Burnett in regarding " the Infu- 

 soria as in a completely transition state; and 

 although it may be well to arrange these forms 

 systematically, for the sake of convenience, yet 

 they cannot be considered as holding fixed zoo- 

 logical positions." * 



* Siebold's Anat. of Invertebr. (Amer. Ed.) 



