146 HIDDEN BEAUTIES OF NATURE 



at fairly regular intervals. These shells, therefore, 

 belong to the kind known as intrinsic. One or 

 two, especially the last, partake of both characters. 

 No. 7, in fig. 41, is a most remarkable specimen, 

 made up of square plates. Its name, although some- 

 what large, is one which any of us might interpret, 

 viz., Quadrula symmetrica. 



All the shells of this illustration belong to the 

 Nebela (Gk. nebel, a bottle) genus. Under the 

 microscope they occasion as much interest as the 

 Difflugia, and are always intensely fascinating, 

 possibly owing to their extreme minuteness. All of 

 them are below the two-hundredth of an inch in 

 diameter! 



To the Nebela belong some of the most beautiful 

 rhizopods known to microscopists. They too are 

 found in marshy ground along with the sphagnum. 

 Sometimes the moist vegetation swarms with speci- 

 mens in full activity ; at other times, in the same 

 locality, under apparently similar conditions as re- 

 gards temperature, light, etc., not a single creature 

 can be found. 



The arrangement of the shells of these mere 

 specks in creation is of a most extraordinary charac- 

 ter. In some we find circular or oval discs, discs 

 that have no relationship in size with that of the 

 shell, large shells having small discs and small shells 

 having large discs. In some the shells are made up 

 entirely of circular, in others of oval discs, while in 

 others they are mixed, and, what is more astonishing, 



