322 BESCBiPTioN OF [Potygastrica 



tured by elegant rows of dotted, imperfectly radiant lines. (l-348th.) 

 ^gina. 



AuLiscTJS polystima = Coscinodiscus polystigma, of the Frisian Sea. 



Genus Bacillaeia, (Ehr.) — Lorica bivalve, or multivalve, in the 

 form of a many-sided prism. Self-division complete ; but the fnistules 

 do not entirely separate at their angles, and thus they form gaping 

 or zig-zag chains (figs. 166 to 170); even when thus connected 

 together they are motile. " The organs of locomotion," says 

 Ehi'cnberg, " are soft peg-like processes, projecting from a longitu- 

 dinal cleft ; in B. tabellaris, transparent polygastric vesicles have 

 been seen. Two openings are visible at the end of the lorica ; 

 hitherto the nutritive organs have not been demonstrated by artificial 

 means. At one time it was supposed these animalcules had no mouth, 

 but were nourished by absorption. Self-division always longitudinal 

 and dorsal, so that the surfaces which hang together are those of the 

 sides. A small deflection and locomotion of the chains is observable 

 in the fresh water species, but is more remarkable in the marine 

 varieties of B. paradoxa, which, when separated, move quickly, like 

 Kavicula. The name Bacilla/ria was first given to them by G. Malin ; 

 botanists gave them the names of Liatoma, Conferva, and Oscillator ia. 

 They form part of the genus Vibrio of Midler." Nageli states, the 

 individuals of this genus possess anucleus. See genus Biatorma (Kiitz.) 



B. paradoxa Vihrio paxillifer (M.) — Lorica straight, slender, stria- 

 ted ; often fifteen times longer than broad. Nine striae occur 

 in l-1200th. It is of a yellow ochre colour, and its locomotion is 

 distinct. In consequence of incomplete self- division, the frustules 

 adhere side by side, and the band-like clusters thus formed are either 

 straight, wavy, or zig-zag, according as they slide one upon another. 

 The individuals forming the chain, can detach themselves, and then 

 move freely about like Nmicula. Group 167 is a polype-like cluster, 

 and fig. 166 a front and side view of a single specimen. Found 

 upon sea-weed. Length 1-1 150th to l-240th. 



B. vulgaris = Diatoma vulgar e (Kiitz.) — Straight ; three or four 

 times longer than broad. It has thirteen transverse stria) in 

 1-1 200th. Fig. 168 is the dorsal view of part of a group of foiu- 

 specimens ; viewed sideways, they resemble a spindle. Found fossil 

 and alive, both in fresh and salt water. In the Ehone, it covers over 

 confer ca ghmcrata, in the form of a thick felt. 



