Bacillaria.] THE INFUSORIA. 221 



consist of two to thirty wands. Length of single wands, 

 or rods, l-570th to l-120th. 



292. FRAGILARIA rhabdosoma (Vibrio tripentatus, M.) 

 The common Fragilaria is smooth, slender, and from five to 

 twenty times longer than it is broad. The extremities of 

 the lateral surface are needle-shaped. In some chains, the 

 specimens are united together firmly ; in others, the bands 

 easily drop to pieces ; the portions afterwards creep in a 

 live manner. They may easily be mistaken for Synedra 

 and Navicula ; but the number and position of the open- 

 ings are the distinguishing marks. Group 1 74 are sepa- 

 rate specimens, and fig. 1 73 a band of them. Found, living, 

 in fresh water, and fossil in the Polirschiefer of Cassel. 

 Length l-570th to l-200th. 



293. FRAGILARIA turgidula. The broad Fragilaria is 

 striated, and from two to three times longer than it is 

 broad, as seen in group 172. In l-100th of a line, there 

 are nine striae. Length 1-1 720th to 1-5 70th. 



294. FRAGILARIA multipunctata. The punctated Fragi- 

 laria is smooth, has slender corpuscles, and is eight to 

 sixteen times longer than broad ; ova of a yellow golden 

 colour, and multipartite. Found amongst conferva. 

 Length l-5?0th to 1 -280th. 



295. FRAGILARIA bipunctata is probably synonymous 

 with rhabdosoma ; it is smooth, and four to five times 

 longer than it is broad. The ova are of a golden-yellow 

 colour, and contracted into the form of two rounded 

 spots. Found near Mount Sinai. Length 1-1 200th to 

 1 -760th. 



296. FRAGILARIA angusta. The narrow Fragilaria is 

 smooth, and five to six times longer than broad; ova of 



