Class II. 1NFUS0KIA. 



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 larva? of certain Flana- 

 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.) 



