AMOEBINA. 903 



the characteristic test (Buck, Cattaneo). Conjugation of Amoebae has 

 been said to occur 1 . 



The formation of colonies, similar to those of Microgromia (p. 892, 

 ante), takes place in a few instances. In Pamphagus. ( Lecythimn) the 

 individuals formed by fission may remain united by a protoplasmic mass 

 from which radiate pseudopodia ; or free individuals may fuse, two or more 

 together (=Gromia socialis^ F. E. Schulze). Platoum stercoreum emits 

 from the aperture of the test a mass of protoplasm, which acquires a test 

 itself; new individuals then bud from the bridge uniting the two. So too 

 in the Plectophrys of Entz. The colonies (Cystophrys oculea) of Diplo- 

 phrys Archeri are probably produced by fission. Encystation is general. 

 In Amoebae stalked brown resting cysts and delicate digestive cysts have 

 been recorded. Cochliopodium bilimbosum forms a thick cyst with outer 

 gelatinous layer. Diplophrys Archeri has a double cyst, an inner smooth 

 membrane, and an outer tuberculate. The Testacea, as a rule, encyst 

 within the test, the aperture of which either collapses (Placocista) or is 

 closed by a diaphragm, sometimes laminated, sometimes containing foreign 

 bodies, e. g. diatom-frustules, algal cells, residues of food, &c. The 

 organism itself contracts, and may have a single-walled cyst or a double, 

 both forms occurring in the same species. In the double cyst of Euglypha 

 the outer cyst is ovate and composed of hexagonal plates, the inner 

 globular and tuberculate. Platoum may quit the test to undergo encys- 

 tation, and a number of individuals may fuse and then encyst like a single 

 individual. 



The Amoebina appear to be cosmopolitan. They are chiefly fresh- 

 water ; Amoebae usually living in mud, &c., Testaceous genera on stones 

 and water plants. Very many of the freshwater forms are found in damp 

 moss ; Amphizonella violacea and a tew Amoebae in earth or sand. Amoebae 

 occur in putrifying solutions, Testaceous forms rarely do so. A few Amoebae 

 are parasitic, both in Vertebrates and Non -Vertebrates. Endamoeba 

 Blattae is a constant inhabitant of the large intestine of the cockroach. 

 An Amoeba has been found associated with a skin disease of sheep in 

 Australia, and in inflammation of the colon in man 2 . Phonergates vorax 

 ( Pamphagus) may live as a parasite in Cyclops, Rotifers, Infusoria, and 

 leaves of plants. 



1 Gruber mentions (Z. W. Z. xli. p. 215) that an Amoeba verrucosa very commonly contains 

 within it a small specimen of its own species which apparently undergoes no change. For a sum- 

 mary of the accounts given of the formation of amoeboid spores, &c., in different Amoebina, see 

 Butschli's Protozoa, pp. 156-61, and the original authorities to which he refers. It is probable that 

 many of them at least are cases of parasitism, probably of Chytridiacea or Schizomycetes. Phoner- 

 gates vorax is said by Buck (Z. W. Z. xxx. pp. 29, 31) to give origin to spores by which animals or 

 plants may be infected. See also note i, p. 900, ante. 



2 The parasitic Amoeba, described by Grassi (Rendic. d. R. 1st. Lomb. (2), xiv. 1881, and Atti 

 Soc. Ital. Sc. Nat. xxiv. 1882), from Sagitta, &c., like the Protomyxomyces of Cunningham (Q. J. M-. 

 xxi) are probably Mycetozoan judging from their reproductive phenomena. 



