EECEEATIVE SCIENCE. 



149 



the divided, but imseparated, incrusted sar- 

 code-globules. One of tlie most common 

 Foraminifera is the Miliola — so called from 



31 33 33 



Opaciue-shelled Foraminifera (Arrangement alter- 

 nately lateral). 

 Fig. 31, Spiroloculina canaliculata, D'Orbigny. 32, 

 Triloculina pulchella, D'Orb. 33, Haaerina com- 

 pressa, D'Orb. (putting on spiral). 



its resemblance to a millet-seed — found abun- 

 dantly in the heaps and ridges of sea-weed 

 left by the receding tides upon the sands. 

 Like the G-romia these have only a single 

 aperture for the extension of the pseudo- 

 podia formed by their extensile flesh, and it is 

 a curious and interesting sight to watch them 

 slowly hauling themselves up and along the 

 transparent sides of a glass tumbler or the 

 walls of an aquarium. 



The Miliola were noticed long ago by na- 

 turalists, who put them amongst the Serpula, 

 or encased sea-worms, on account of their 

 appearing to be folded tubes, in like manner 

 as the Rotalia and other similar forms were 

 described in books as minute Nautili; and it 

 was not until 1835 that Dujardin showed 

 their true position in the animal scale as 

 Rhizopods, or root-foot animals. 



The Foraminifera are all marine, and 

 every zone of sea-depth has its peculiar 

 species or varieties — the deepness or shal- 

 lowness of the region in which they exist 

 often causing very considerable differences 

 in the appearance of the individuals; thus the 

 JRotalia repanda grows large and thick — so to 

 speak of a microscopic sheU — in shallow seas, 

 and becomes flattened when obtained from 

 deeper water. Another kind, the Glohigerina 

 hullo'ides, on the contrary, becomes dwarfed 

 and small in shallow water, but grows large 

 and abounds in deep-sea regions. 



In the abysses of the ocean these micro- 



scopic shells constitute almost the only ma- 

 terial of its oosy bed. In the soundings made 

 for the Atlantic Telegraph, the lead brought 

 up, in regions beyond the range of earthy 

 sediments brought by currents, from depths of 

 three miles, whitish clayey mud all but wholly 

 composed of Globigerinse. 



In the blackness and stUlness of those 

 enormous depths, extracting the minutest 

 particles of lime from the dense waters, these 

 little beings live in myriad hosts, and, tiny 

 as they are, accumulate in slowly passing ages 

 into enormous masses of calcareous strata, con- 

 vertible, idtimately, into limestone, as Time, in 

 his endless circles, shall bring round another 

 change of land and sea, and the bottom of 

 the deep shall be converted into the mountain 

 range. 



Thus, too, the Foraminifera have played, 

 in geologic ages, a like important part in the 

 formation of the rock-beds of the earth's 

 stony crust. !No organic creature, large or 

 small, has contributed so much material : 

 every limestone, every sandstone, every clay, 

 from the silurian epoch to the present hour, 

 offer the evidences in their remains. A 

 certain green sandy clay, of silurian age, in 

 Russia, is constituted, in great part, of sand, 

 the particles of which are stony casts or 

 moulds of the chambers of Foraminifers, like 

 as the sand dredged to-day in the Gulf of 

 Mexico consists of silicate of iron modelled 

 in the cavities of such microscopic shells. 

 The mountain-limestone— so beautifully stud- 

 ded with coral-branches, and encrinital stems 

 — abounds with their tiny carcases. A Rus- 

 sian limestone of the same age is wholly 

 composed of Fusilina, and other small forms ; 

 while similarly constituted rocks occur in 

 America, and in the Arctic regions. 



The oolitic freestones have generally a 

 Foraminifer in nearly everyone of those sphe- 

 rical egg-like grains (from which they derive 

 their geological name), like as is found in the 

 sand-grains on the shores of modem coral- 

 reefs. The white chalk is, as we have already 



