18 PROTOZOA— RHIZOPODA phvlu.m i 



Order 2. FORAMINIFERA dOrbigny. 



Rhizopoda usually with a test ivhich is typically calcareous hut may he siliceous 

 or agglutinated ; consisting of one or more chamhers ; pseudopodia reticulate. 



The Foraminifera are for the most part minute animals varying in size 

 from a fraction of a millimetre to several millimetres in length, but may 

 develop a test several inches across ; these, however, are rare exceptions. A 

 few species occur in fresh or brackish water, but the great majority live in 

 the ocean. They are found at all depths, but are most frequent at moderate 

 depths in the ocean basins, where they form characteristic deposits — the 

 so-called "globigerina ooze." In the vicinity of tropical coral islands many 

 species occur in great abundance. 



The animal itself is a single-celled form with one or many nuclei, as will 

 be later explained. The test, in many cases at least, is really an internal 

 structure, as the thin film of protoplasm which covers it in the perforate 

 forms, and probably in others, is capable of secreting the material of the test 

 to repair fractures and the like. 



nature. Huxley (Journal Microscop. Science, 1868, YIII. No. 6) and Haeckel (Jeuaische Zeit- 

 scbrift, 1870, V. 3, p. IS) regarde<l them at first as portions of Bathi/bius, and designated 

 them coccoliths (Fig. 1). The simple, disklike varieties, convex on the upper side and concave on 

 the lower, were termed discoliths (Fig. 1, c) ; while those composed of two closely applied disks 

 of different sizes, resembling cuff-buttons in profile, were referred to as cyatholiths (Fig. 1, a, b). 

 Coccoliths are only visible umler powers of 800 to 1000 diameters, and exhibit, as a rule, a number 

 of zones differing in their retractive indices, which are disposed about a single, double or star- 

 . , , ,, g shaped central granule. Fre- 



^.JL-^^ quently large numbers of cocco- 



yr,,^^-^^v. %p Wihs become aggregated to- 



W H^^^^^ \ gether in the form of freely 



suspended spherules or cocco- 



a i -Will Ml l|U|' ^'' 



i #«vil m ll\ ^K/§g?^.'S'J.^2^ x^/^ spheres {Fig. 2). Besides cocco- 



i-.iisy vv vj ASS-^ri?^ ^ liths, other minute, rod-shaped, 



'. 5 m©//i mil fill \^^, 



calcareous bodies are sometimes 



Fro. l,rt, ;;.—Coecoi(7/is (6V-t//(o/(7/(x) from the Atlantic Ocean ; upper sur- met with, which are charac- 



face and in prottle (after Haeckel) . ^ . .. ,- terised by a discoidal or cruci- 



Fio. 1, c.—Cocxoliths (Disrohths) from the Adriatic bea ; upper surface <•„„,„ „„i„„„„„ „ *. 4. i 



and in protile (after O. ScliniKlt). form enlargement at one end. 



Fio. 2.— Cocco-fji/icces fiom the Atlantic Ocean (after Haeckel). inese are called rhabdoliths 



Fio. 3.— iJ/i«Mn/it/is from the Adriatic Sea (after O. Schmidt). All figures (Fig. 3), and their nodular 



iiias^nilied 70(1 diameters. aggregations r/uthdospheres. 



Wyville Thomson, Carter and 

 Murray would identify coccospheres as unicellular algae, or as sporangia of algae, while Haeckel 

 creates for them a special group, '' Calcocytae" and assigns them provisionally to the Protophytes. 

 According to Harting, however, the action of ammonia generated by the decomposition of albumin- 

 ous matter held in solution in lime sulphate or lime chloride, causes the separation out of minute 

 calcareous disks which bear a striking resemblance to coccoliths. Hence it would appear that 

 the formation of excessively fine divided particles of lime in the sea should take place wherever 

 there are decomposing albuminous or nitrogenous substances present, and the calcium sulphate 

 held in solution in the water becomes precipitated as calcium carbonate. 



^ Literature: d'Orbigny, A., Foraminiferes fossiles du bassin tertiare de Yienne. Paris, 1846. 

 — Ehrenherg, O. O., Mikrogeologie, 1854, and Abhaiidlungen der Preu.ss. Akad. Wi.ss., 1839. — 

 Schidtze, Max, Ueber den Orgauismus der Polythalaiiiien. Leipzig, li^A.-^Cuipenter, W. B., 

 Introduction to the Study of the Foraminifera. Ray Society, \^Q2.—Reuss, E. A., Numerous 

 Reports in Sitzungsberichte der Wiener Akademie, from 1860 onwards. — Schwager, Conrad, 

 Saggio di una classificazione dei Foraminiferi. Boljet. Coniitato Geol., 1876. — Brady, W. B., 

 Monograph of Carboniferous and Permian Foraminifera. Palaeontograph. Soc, 1876. — Brady, 

 IF. />'?, Report on the Foraminifera, Scieut. Results Challenger Exped. , Zoology, XL, 1884. — 

 Sherborn, V. />. , Index to the Genera and Species of the Foraminifera. Smith. Misc. Coll., 

 1895, vol. xxxvii. — Egger, J. G., Foraminiferen der Seewener Kreideschichten. Sitzber. Bayer. 

 Akad. Wi.ss., 1909, No! 11. — Schelhoien, E., Monographic der Fusulinen. Palaeontogr. 1908-1912, 

 vols. Iv., lix. 



