Naviculacea.'] infusortal animalcules. 373 



from a cleur central spot, and extending to the marginal zone. (P. ;3, f. 

 131, and P. 14, f. 26.) Diameter l-860tli to l-GOOth. 



Gaxltoxella moniliformis. — Smooth, large, cylindrical, short ; ends 

 truncated cones ; when single, and viewed from the back, they appear 

 octagonal ; contents greenish. In sea water ; often confounded with 

 G. Uneata. Size 1 -860th. 



G. aurichaJcea. — Segments cylindrical and slender ; their length 

 full twice the diameter, with either a single or two perforated rays 

 contiguous at the middle ; the ova are green, but, when di-ied, become 

 of a golden-yellow colour. Thickness 1 -2300th to l-1720th. In 

 fresh water, ditches, and slow streams. 



G. ferniginea = Melosim ochracea (Ralfs.) — Slender, oval, 

 convex at both ends ; smooth. In many, perhaps in all chalybeate 

 waters, and also in peat water, which contaias a small proportion of 

 iron, this is to be found ; it is of the colour of iron-rust, and in 

 mineral springs, in which it abounds, is often taken for precipitated 

 oxide of iron. It covers every thing under water, but forms so 

 delicate and floccose a mass, that the least motion dissipates it. In 

 the spring of the year, this mass is composed of very delicate pale 

 yellow globules, which can be easily separated from each other. 

 They unite together in rows, likeJfehort chains, and produce an irre- 

 gular gelatinous felt or floccose substance. About summer, or in 

 autumn, they become developed into more evidently articulated and 

 stiff threads, of a somewhat larger diameter, but still form a com- 

 plicated mass or web, and, either from adhering to each other or to 

 delicate conferva, appear branched. In the young condition, when 

 examined under shallow magnifiers, they resemble gelatine ; but with 

 a power of 300 diameters, the flexible granules are discoverable, and 

 with dexterous management, the little chains forming the felt or 

 floccose web can be made out. In summer, on the other hand, its 

 structure can be observed much more easily and distinctly. Early 

 in spring, the coloiu" is that of a pale yellow ochre ; but in summer^ 

 that of an intense rusty red, (P. 2, f. 129 and 130.) Diameter 

 1- 1200th 



According to Kiitzing, this is not a species of GaUioneUa, but a 

 Conferva; it has no true siliceous lorica, as have true Diatomece, 

 and the coating of oxide of iron is not an essential element, but 



