AMOEBINA. 897 



Quart. Journal Geol. Soc. xxxviii. 1882. Parkeria, Loftusia, W. B. Carpenter and 

 Brady, Ph. Tr. 159, 1869; Loftusia, Dawson, Quart. Journal Geol. Soc. xxxv, 

 1879; cf. Carter, A. N. H. (4), xix. 1877. Orbitoides, Martin, supra. 



Dimorphism : Brady, Challenger Reports, ix. supra, p. viii ; Munier-Chalmas on 

 Nummulites 2o\& Assilina, Bull. Soc. Ge'ol. France (3), viii. 1881 ; De la Harpe, ibid, 

 ix. 1882 ; Munier-Chalmas and Schlumberger on Miliolinae, A. N. H. (5), xi. 1883; 

 Id. 'Miliolides trdmatophorees,' Bull. Soc. Ge'ol. France, (3), xiii. 1885. 



Chemical composition of test : Brady, Challenger Reports, ix. supra, pp. xvi-xxi. 

 Structure of protoplasm, Biitschli, M. J. xi. 1886. Nuclei : Id. ibid. : R. Hertwig, 

 J. Z. x. 1876, xi. 1877, pp. 345-7 ; F. E. Schulze, A. M. A. xiii. 1877, p. 9 ; Gruber, 

 Z. W. Z. xl. 1884, pp. 127-8; Multi-nucleate Gromia, Max Schultze, A. M. A. ii. 

 1866, p. 140. 



Reproduction: W. B. Carpenter, &c., 'Introduction,' supra, pp. 37-8 with ref.; 

 Id. on species of Orbitolites, Challenger Reports, vii. p. 16 ; Peneroplis (and Orbu- 

 lina\ Schacko, A. N. 49, 1883; Cristellaria, Brady, Challenger Reports, ix. supra, 



P- 543- 



Conjugation^, Gervais, C. R. xxv. 1847, p. 467. 

 Symbiotic algae, &c., Biitschli, M. J. xi. 1886, pp. 93-9. 



CLASS AMOEBINA. 



Rhizopod Protozoa with lobose, digitiform or filose psetidopodia, some- 

 times branched, rarely anastomosing, either locomotor and alimentative in 

 fimction or the latter alone, sometimes perhaps tactile. The presence of a 

 hyaline border ('ectosarc'} depends on the density of the protoplasm. The body 

 is either naked, enveloped in a complete gelatinoid or chitinoid coat, or lodged 

 in a monothalamous test with one or two apertures, in composition either 

 gelatinoid, chitinoid, encrusted with foreign bodies, or made up of chitinoid 

 or siliceous plates cemented together. Non-cotitractile vacuoles are sometimes 

 present in numbers ; contractile vacuoles, sometimes absent, are usually single, 

 or limited to a few. There may be one, two, or many nuclei. Freshwater, 

 terricolous, rarely marine, saprophytic, or parasitic. 



It has been shown that in the naked Amoebina with dense proto- 

 plasm, a superficial thin layer undergoes coagulation by contact with the 

 water in which the animal lives, but that it is continually dissolved in 

 locomotion and as continually formed anew. The degree to which it is 

 specialised is variable in different species ; when more resistent than usual 

 it causes puckers and lines on the surface, e.g. in Amoeba verrucosa, and 

 conular eminences at the bases of the pseudopodia, e.g. A. tentaculata. 

 In a few instances however a permanently differentiated layer or cuticle 

 is met with. Zonomyxa has a chitinoid (?) resistent membrane which is 

 stretched out to invisible thinness where the protoplasm is in motion or 

 protruded as pseudopodia ; Amphizonella violacea is clothed with a gela- 

 tinous coat pierced by the pseudopodia ; Trichosphaerium, with an invest- 



3 M 



