18 PROTOZOA—RHIZOPODA CLASS I 
Order 1. FORAMINIFERA. dOrbigny.’ 
(Polythalamia, Breyn ; Thalamophora, Hertwig.) 
Rhizopoda with slender, thread-like, or band-like, frequently anastomosing pseudo- 
podia, and usually with a calcareous, more rarely with an arenaceous or chitinous test. 
The scarcely differentiated, richly granulated sarcode body of the 
Foraminifera usually contains a contractile vacuole, and is enclosed by a shell 
or test which is almost invariably calcareous in composition, although in some 
cases it may be of a silicious or even chitinous nature, and which, as a rule, is 
divided into chambers by interior partitions or septa. The sarcode com- 
municates with the extericr either by means of a single large aperture (oral 
or general aperture) situated at one extremity of the test, or by means of 
innumerable fine pores (foramina) which perforate the shell. Through these 
openings the sarcode emits usually long, filiform, net-like anastomosing 
pseudopodia, in which often active granular currents are discernible. 
Only a few forms secreting chitinous tests (Gromia) are fresh-water inhabit- 
ants; the rest are marine in habit. Foraminifera are usually so small in size 
that, although perceptible to the naked eye, they can barely be discriminated 
as separate individuals. Certain exceptionally large forms (Nuwmmulites) attain 
a diameter of four or five centimetres. 
intermingled with decomposed organic matter. In deep-sea ooze, which consists chiefly of lime 
carbonate, as well as in Bathybius, great quantities of minute calcareous bodies of various shapes 
are found, such as also occur as an essential constituent of chalk, marls, and most marine lime- 
stones belonging to older geological periods (cf. C. W. Giimbel, Neues Jahrbuch fiir Mineralogie, 
1870, yp. 753). Ehrenberg 

ie 2 2 termed these bodies morpho- 
(ee lites, and regarded them as 
iO} inorganic in nature. Huxley 
r) (Journal Microscop. Science, 
) a 1868, VIII. No. 6) and Haeckel 
J (Jenaische Zeitschrift, 1870, 
eaRge h V. 3, p. 18) regarded them at 
iS gde tee eee 4 _, first as portions of Bathybius, 
CoS ar ny Pe Si aia from the Atlantic Ocean ; upper side and designated them coccoliths 
Fic. 1, e.—Coccoliths (Discoliths) from the Adriatic Sea; upper side and (Fig. 1). The simple, disk- 
in profile (after O. Schmidt). like varieties, convex on the 
Fic. 2.—Coccospheres from the Atlantic Ocean (after Haeckel). - 
Wig. 3.—Rhabdolithe from the Adriatic Sea (after O. Schmidt), av UPPer side and concave om the 
figures magnified 700 diameters. lower, were termed discoliths 
(Fig. 1, a, b); while those com- 
posed of two closely applied disks of different sizes, resembling cuft-buttons in profile, were referred 
to as cyatholiths (Fig. 1, ¢). Coccoliths are only visible under powers of 800—1000 diameters, and 
exhibit, as a rule, a number of zones differing in their refractive indices, which are disposed about a 
single, double, or star-shaped central granule. Frequently large numbers of coccoliths become 
aggregated together in the form of freely suspended spherules or coccospheres (Fig. 2). Besides 
coccoliths, other minute, rod-shaped, calcareous bodies are sometimes met with, which are charac- 
terised by a discoidal or cruciform enlargement at one end. These are called rhabdoliths (Fig. 3), 
and their nodular aggregations rhabdospheres. 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 albuminous 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 decom- 
posing albuminous, or nitrogenous substances present, and the calcium sulphate held in solution in 
the water becomes precipitated as calcium carbonate. 
1 Literature : 
@ Orbigny, Alcide, Foraminiferes fossiles du Bassin tertiaire de Vienne, 1846. 
