NATURE'S JEWELS. 177 



fairing in the Diatoms are beyond description, yet 

 they all exist under a few general characteristic 

 forms. Thus they are attached to each other by a 

 stalk or pedicle, or coherent in chains and branching 

 tufts, or isolated and free ; and under these several 

 forms or conditions of existence they assume an 

 endless diversity of figure and markings, which to 

 describe in detail far surpasses our skill. A few 

 words strung together may, however, give some 

 general idea of these diversities. 



Thus as to their figures : they are wand-like, 

 trapezoid, square, round, circular or like a pill-box, 

 globular or spheroid, boat-shaped, oval, egg-shaped 

 or ovoid, discoid, wedge-shaped, cuneate, triangular, 

 rectangular, curved, twisted, sigmoid or undulate, 

 arcuate, saddle-shaped, geniculate, alate or winged, 

 lunate, &c., &c., &c. 



Then as to the symmetrical designs or mark- 

 ings on the valves, some are hexagonal, others are 

 marked in lines of round or oval dots. The mark- 

 ings on the discoid forms are generally the most 

 beautiful, and in some the pattern is divided into 

 six, eight, or ten compartments, all arranged round 

 a common centre, and beautifully ornamented with 

 M 



