5 8 PROTOZOA CHAP. 



faeces of several mammals. The best monograph of this group 

 is that of Penard.^ 



2. FOEAMINIFERA ^ 



Sarcodina with no central capsule or distinction of ectosarc ; 

 the pseudopodia fine, branching freely, and fusing where they meet 

 to form protoplasmic- networks, or the outermost in the pelagic 

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

 times dimorphic, reproducing hy fission and hy rhizopod or 

 flagellate germs in the few cases thoroughly investigated : all marine 

 (ivith the exception of some of the Allogromidiaceae), and usually 

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

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

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

 hy minute pores 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 the 

 " 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 characterisations 

 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 think 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, gelatinons, or formed of cemented particles, wliether 

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



^ Faune Rhizopodique du Bassin du Liman, 1902. See also Cash, The British 

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



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

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



* Challenger Reports (Zool.), vol. i.v. 1884. 



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

 and Fickert in Z. wiss. Zool. Ixv. 1899 ; Rhnmbler in Lang's Protozoa, 1901 ; 

 and for a full synopsis of genera and species, " Systematische Zusammenstellung 

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



