Infroducficni to Am' Dial AlorpJwIogy. 55 



the primary spiral. 14th. Nummulitidae — finely perforate, 

 with a special septal plane differentiated from the rest 

 of the shell, without the ordinary tubular structure. Each 

 chamber wall is complete in itself, ex. Archseodiscus, Poly- 

 stomella,^' Nummulites, Orbitoides, Fusulina } 



Probably these are not true families, as outward characters 

 are variable, and passage forms are numerous.! 



Class 4. Flagellata (Ehrenberg). — Nucleated plas- 

 tides, each moving by a long, permanent, whip-like 

 process; reproducing by fission or gemmation ; motion 

 is by swimming or rolling (Doxococcus), 



They are divisible into two orders: — ist. Monadina — 

 minute, vacuolated forms, with no differentiated ectosarc, and 

 simple flagella. These comprise two families: — ist. Mo- 

 nadidaj — having a constant shape ; reproducing by longitu- 

 dinal or transverse fission ; with one flagellum (Monas), or two 

 (Glenomorum) ; sometimes with a red speck (Microglena) ; 

 some are pear-shaped with a thick tail (Bodo), or the monads 

 may be in clusters, each with two flagella (Uvella). In 

 Anthophysa they are stalked, and have a contractile vesicle, 

 and in Polytoma the clusters of monadiform spheres produced 

 by incomplete division are within a hyaline cuticle. There 

 may be an oval (Cryptomonas) or a flask-like lorica 

 (Lagenella). Trichomonas has a few cilia as well as two 

 flagella. 



Fam. 2nd. Astasiidae, with no lorica and a variable shape. 

 Colacium is parasitic on crustaceans ; others are free, with no 

 red speck (Astasia), or with one (Euglena) or two (Diselmis). 

 Peranema is rounded, tapering to the flagellum, with colour- 

 less granules and vacuoles within a thin cell-wall. There 

 may be several (Polyselmis), or two equal (Zygoselmis) or 



* Sometimes separated as a family Polystomellidoe. 



t D^ Orbigny^s classification is embodied in a note on a former page : it 

 takes for its basis the modes of budding. Schultze divided them on the 

 same ground into Soroidea, Rhabdoidea, and Helicoidea, 



