304 



THE MICROSCOPE. 



characters. Again, the Astasia of the former is the Eu- 

 glenia of the latter ; and so on with many other families 

 of the Polygastrica Infusoria, which by the labours of later 

 investigators have undergone a complete revision ; and in 

 their classification, some have been degraded to the vege- 

 table kingdom, as the Desmidiacece, Volvocinece, &c., 

 whilst others have been advanced a step higher in the 

 animal series ; none having excited so much controversy, 

 or received so much attention from microscopists, as 

 Desmidiacece and Diatomacece. The first of these we have 

 already disposed of, in our remarks oil the vegetable 

 kingdom, where we must be content to leave them for the 

 present j not so the Diatomacece, which offer many interest- 



Fig. 177. 



1 Dtatoma vulgare. 2, Achnanthidum lineare. 3, Amphitetras antediluviana. 

 4, Orthosira spinosa. Front view, with globular and oval forms. (From 

 Springfield, Barbadoes.) 



ing structural characteristics, of sufficient importance to 

 warrant us in keeping them in the animal division. They 

 are, indeed, most striking objects under the microscope, 

 from the peculiarity, beauty, and variety of their forms, 

 from their bilateral symmetry, external markings, and 

 indestructible siliceous skeletons; that we believe they 



