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 encystation, and a number of individuals may fuse and then encyst like a single individual.

The Amoebina appear to be cosmopolitan. They are chiefly freshwater; Amoebae usually living in mud, etc, Testaceous genera on stones and water plants. Very many of the freshwater forms are found in damp moss; Amphizonella violacea and a lew 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 man2. Phonergates vorax ( - Pamphagus)may live as a parasite in Cyclops, Rotifers, Infusoria, and leaves of plants.

1Gruber 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 summary of the accounts given of the formation of amoeboid spores, etc, in different Amoebina, see Biitschli'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. Phonergates 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 1, p. 900, ante.

2The parasitic Amoeba, described by Grassi (Rendic. d. R. 1st. Lomb. (2), xiv. 1881, and Atti Soc. Ital. Sc. Nat. xxiv. 1882), from Sagitta, etc, like the Protomyxomyces of Cunningham (Q. J. M. xxi) are probably Mycetozoan judging from their reproductive phenomena.

Hallez has described by the name of Arcyothrix Balbianii an Amoebine found by him in a vessel containing ova of Ascaris megalocephala, kept at 25°C. It moves upon a pedal disc, is in shape irregularly globular, has non-contractile vacuoles and one contractile, with pseudopodia of two kinds, an anterior, digitiform, by which food is captured, and two posterior. The latter are of great length and extreme tenuity, beset with minute varicosities, and as a rule bifid. They are usually directed in opposite directions, and Hallez thinks they serve like a moveable net to retain the food. See Mem. de la Societe' des Sc. etc, Lille, (4), xiv. 1885. With Arcyothrix may be compared Podostoma filigerum, a freshwater amoeboid form, which possesses, in addition to ordinary pseudopodia, one or two long vibratile processes used for catching food. See Claparede and Lachmann, Etudes sur les Infusoires, etc, Paris, i. 1858-9, p. 441; Cattaneo, Atti Soc. Ital. Sc. Nat xxi. 1879.

Catallacta

Under this name Haeckel has described a marine organism, Magosphaera planula, found by him in 1870 on the coast of Gisoe, a Norwegian island some miles S. W. of Bergen. His account may be briefly summarised as follows, (i) Egg-like stage; in the form of spherical cysts .07mm. in diameter, attached to the stem of the Alga Cladophora. The cyst-membrane is tough, indistinctly laminated, and at the point of attachment either thin or perforated. The contained protoplasm is yellowish; there is a vesicular nucleus surrounded by a zone of granules, often disposed in radiating processes, (ii) Segmentation stage. The nucleus and protoplasm undergo binary fission with successive stages, 2, 4, 8, etc, until thirty-two cells are formed. The cells, at first globular, become polygonal from mutual pressure, and are arranged in a single layer. Their outer surfaces give origin to pseudopodial processes which are finally converted into cilia. The sphere now rotates within the cyst, (iii) Volvox stage. The sphere is free-swimming, •07mm. in diameter. Its constituent cells are pear-shaped, their outer surfaces convex and ciliated, their inner ends attenuated and united centrally; they are imbedded in a clear structureless jelly. Each cell has at its base a slowly pulsatile vacuole.

The vesicular nucleus surrounded by granules is median in position, (iv) Peritrichous Infusorian stage. The cells are detached, and swim about by means of their cilia. The body of the cell shortens, lengthens, bends from side to side. The contractions of the vacuole are more rapid. The ciliated disc is seen to be vertically striated, and particles of carmine brought to it by the cilia are ingested, (v) Amoeba stage. The cells become amoeboid. The Amoeba is characterised by its sharp-pointed pseudopodia protruded singly or in bundles. From time to time a pseudopodium elongates and vibrates slowly. There is a hyaline ectosarc. Carmine particles are ingested at any point of the surface. Haeckel did not succeed in tracing the life-history beyond this stage. But he found creeping over the Cladophora Amoebae of various sizes, with pseudopodia of identical character. The nucleus of the larger Amoebae was as large as that of the egg-like stage. The contractile vacuoles were increased in number, the largest specimen observed having five. The Amoebae in question were crammed with diatom-frustules, chlorophyl-bodies, etc. Haeckel supposes that they encyst, and the life-history, as above-detailed, recommences.

If this supposition is correct, the dominant phase is an Amoeba, and Magosphaera can scarcely be classed with Flagellata as it is by Saville Kent. The organism does not appear to have been seen by any subsequent observer. See Haeckel, J. Z. vi. 1871;

Saville Kent, Manual of the Infusoria, i. p. 322-4; Allman, J. L. S. xiii. 1887, P. 435The Amoebina may be classified as follows: I. Nuda s. Gymnamoebae: devoid of a test; in some instances there is a coagulated superficial pellicle, or a complete gelatinoid, chitinoid, or spinulose coat; pseudopodia lobose, pointed, etc.