Bacillaria.] the infusoria. 199 



face, resembles a coin. It is fragile and incombustible; 

 that of G. ferruginea appears to be silicate of iron. A 

 coloured and divided mass of ova (clustered like grapes) 

 is seen internally, as also colourless vesicles or stomach- 

 cells. Change of place has not been seen. They appear 

 to me closely to resemble minute Algae, and are so con- 

 sidered by botanists. Nearly all the species are found in 

 a fossil state and living ; in the former they are exquisite 

 objects for the microscope, under a deep power and proper 

 illumination. 



211. Gallionella lineata. The striped Gallionella is 

 cylindrical, the ends connecting them together being com- 

 pressed, as shewn in the engraving, fig. 128, which is part 

 of a chain, consisting of four individuals, highly magnified. 

 The parts forming the chain are striated longitudinally ; 

 the ova are either yellow or green. It is found in sea- 

 water, and a single chain sometimes measures three inches 

 in length, and is composed of from 1200 to 4000 animal- 

 cules. Length of single individual 1- 1400th to 1 -430th. 



212. Gallionella nummuloides. The spherical Gal- 

 lionella resembles the preceding species, but has its ends 

 convex, so that a single animalcule is almost globular. 

 They are smooth, and the ova is of a yellowish-green 

 colour. Size l-l700thto l-860th. 



213. Gallionella varians. The changing Gallionella 

 is cylindrical, with flat ends ; when separate and short 

 they rest upon the ends, and appear like a coin. In this 

 position, under a good power, delicate radiating striae may 

 be seen, as in fig. 131*; the ova are yellow or greenish. 

 They are found both fossil and recent ; the former are the 

 principal part of the beds of white powder used for 



