Bacillaria.] THE infusoria. 213 



tated ; one of them has four openings, two at each end. 

 Their mode of propagation is simple and complete ; hence 

 they never occur in chain-like clusters, but are always 

 single or in pairs. Thirteen species are known — three 

 living forms, and ten fossil. The first are closely allied 

 to the genus Navicula, but they have no central opening, 

 and from the pecuhar shape of the lorica, like the Coccus, 

 they can crawl about Algae, and indeed are parasitical 

 upon them. 



260. EuNOTiA turgida. The swollen Eunotia has a 

 semi-lanceolate lorica, truncated at the ends, and striated ; 

 these striae are so close together that eight are contained 

 in the space of the 1-lOOth part of a line. A longitudinal 

 furrow runs along the middle of each side ; these are 

 carcely visible in living specimens, owing to the colour of 

 the body. In group 157, three of them are shewn crawling 

 upon a piece of Conferva rivularis. Fig. 158 is a speci- 

 men undergoing longitudinal self-division, as seen under a 

 magnifying power of 600 times. Fig. 160 is the lower or 

 ventral valve of the lorica separated, and shewing the 

 openings at the ends and striae; and fig. 159 a side view 

 of it. Fig. 161 is an end view. Found upon vaucheria 

 and conferva. Length 1-1 150th to 1 -240th. 



261. Eunotia Westermanni. Westermann's Eunotia is 

 striated, and has a semi-lanceolate oval lorica, with ten 

 striae in each 1- 100th of a line. It is of a rich ochre 

 colour. In group 157 those figures marked with a cross 

 represent this species on a piece of coiHlerva. Found 

 with the preceding. Length 1-1 150th to l-480th. 



262. Eunotia zebra. The zebra Eunotia is striated, 

 and of a semi-lanceolate oblong form, with five transverse 



