282 RAMBLES OF A NATURALIST. 



Three Classes. Exaiuples. 



'Echinodermata Sea-urchins, Star-fishes, Ho- 

 lothurias. 

 Sub-division of the Acalephse - Jelly-fishes, Beroes, Stepha- 

 Radiated <| nomias. 



Zoophytes. I Polypi - Coral-animals, Sea Anemo- 



nies. Fresh-water Hy- 

 1^ dras. 



Two Classes. 

 Sub-division of the | p^^ .^^^.^ . r^^^ g^^^^^^^ 



ZooPHTTEr J Iiifiisoria.* - Monads, Volvoces, Amoeba. 



Note II. 



The Rotifers of which we have spoken were discovered 

 by Leuwenhoeck, who was the first to recognise the sin- 

 gular property which these animals possess of alternately 

 dying and being resuscitated, according as they are 

 dried or provided with the water necessary for the main- 

 tenance of their vitality. These Rotifers have become 

 the type of a class, which is already very numerous and 

 of which many species, undergoing the same conditions 

 of life, also possess the same faculties. Besides these 

 Rotifers, the Tardigrades, which belong to the Acari, and 

 are consequently included in the class of the Arachni- 

 dans, and certain Paste-eels, which belong to the Helmin- 



* The place at present assigned by zoologists to the Infusoria 

 must be regarded merely as provisional. The extreme minuteness 

 of these animals renders their study very difficult, and it is daily 

 becoming more probable that this group is far from being homo- 

 geneous, and that it contains a great number of organisms (minute 

 vegetable forms, larval worms, &c.) which have nothing in common 

 except their smallness. The most important modern contributions 

 to the history of the Infusoria, are those of Ehrenberg and 

 Dujardin, especially Ehrenberg's splendid volume, entitled Die 

 Infusions-Thierchen, Berlin, 1838, and Dujardin's Histoire des 

 Infusoires, Paris, 1841, published in the Suites a Buffon. 



