58 PROTOZOA 



faeces of several luanimals. The best iiiouograph of this group 

 is that of Penard.^ 



2. FORAMINIFEltA" 



SarcocUna vnth no central capsule or distinction of ectosarc ; 

 the 'pseuclopodia fine, hranching freely , and fusing ivhere they meet 

 to form protoplasmic netivorks, or the outermost in the pelagic 

 forms radiating , hut vjithout a central or axial filament : some- 

 times dimorphic, reproducing ly fission and hy rhizopod or 

 fiagellate ger7ns in thefeio cases thoroughly rnvestigated : all marine 

 {with the exceptioji of some of the Allogromidiaceae), and usucdly 

 provided with a test of carbonate of lime (" vitreous " calcite, or 

 " porcellanous" aragonite?), or of cemented particles of sand 

 (" arenaceous ") ; test-tvall continuous, or with the walls perforated 

 hy minute p)ores or interstices for the protrusion of pseudopodia. 



The classification of Carpenter (into Vitreous or Perforate, 

 Porcellanous or Imperforate, and Arenaceous), according to the 

 structure of the shell, had proved too artificial to be used by 

 Brady in the great Monograph of the Foraminifera collected by tlie 

 "Challenger" Expedition,^ and has been modified by him and others 

 since then. We reproduce Lister's account of Brady's classifica- 

 tion.^ We must, however, warn the tyro that its cliaracterisations 

 are not definitions (a feature of all other recent systems), for rigid 

 definitions are impossible : here as in the case, for instance, of 

 many Natural Orders of Plants, transitional forms making the 

 establishment of absolute boundaries out of the question. In 

 the following classification we do not tliink it, therefore, necessary 

 to complete the characterisations by noting the extremes of 

 variation within the orders : — 



1. Allogromidiaceae : simple forms, often fresh-water and similar to Rhizo- 

 poda ; test 0, or chitinous, gelatinous, or formed of cemented jiarticles, Avhetlier 

 secreted platelets or ingested granules. Biomyxa, Leidy = Gymnophrys, Cienk. ; 



^ Fmme Bhizopodique du Bassin du Livian, 1902. See also Cash, The British 

 Freshwater Rhizopoda and Heliozoa, vol. i., Kay Society, 1905. 



'^ Chapman, The Foraminifera, London, 1902; Lister, "Foraminifera" in Lan- 

 kester's Treatise on Zoology, pt. i. fasc. 2, 1903. 



^ Challenger Reports (ZooL), vol. ix. 1884. 



* In Lankester's Treat. Zool. pt. i. fasc. 1. For other classifications see Eimer 

 and Fickert in Z. tviss. Zool. Ixv. 1899 ; Rhumbler in Lang's Protozoa, 1901 ; 

 and for a fnll synopsis of genera and species, " Systematische Zusanimenstellung 

 der recenten Reticulosae " (pt. i. only), in Arch. Prof. iii. 1903-4, ]i. 181. 



