ORDER I FORAMINIFERA 21 
phery as fine pores (foramina), are either all equal in diameter, being extremely 
small and closely set together (Fig. 7, 4), or are larger in calibre and more 
widely separated from one another (Fig. 7, 6). Certain vitreous, perforate 
Foraminifera are still further provided with coarser, anastomosing canals, 
which are restricted to definite parts of the shell, such as the septa, or the 
median plane of the 
spiral, in forms which 
are symmetrically con- 
voluted. In the living 
state, these larger canals 
are occupied by bands or 
stolons of sarcode, but 
there is no connection 
between them and the 
other foramina or radial 
tubules. In many forms 
exhibiting more com- 
plicated structure,  cal- 
careous deposits are ob- 
served, which are dis- 
tributed partly over the 
periphery, and partly in 
cavities and depressions 
within the shell itself. 
This is the so-called in- 
termediate or supplemental 
skeleton, which often 
gives rise to peculiar 
excrescences on the peri- 
phery (Fig. 9), and in 
some cases is also pierced 
by tubules. 
Reproduction in the 
Foraminifera takes place 
either by means of fission, 
or by means of small 
nuclei which originate Deep-sea ooze magnified 700 diameters. 4, Bathybius with Coccoliths ; 
within the parent-indi- b, Individual Discoliths and Cyatholiths ; ¢, Coccospheres ; d, Globigerina ; 
$ rn e, Globigerina with bursted test; f, Teatularia, g, g’, Radiolaria; h, %, 
vidual, invest themselves Diatoms; k, 1, Sponge spicules ; m, Mineral fragment. 
with unilocular or multi- 
locular tests, and forthwith abandon the parent shell, whereupon the latter 
falls to pieces. 
The vast majority of Foraminifera are marine in habit. They occur in 
shallow water bordering the coasts, sometimes attached to algae, sometimes 
creeping on the bottom. A few genera are extraordinarily abundant in the 
open sea, occurring at different depths as free-swimming forms, and also on the 
floor of the ocean. Enormous quantities of their remains are spread over large 
tracts of the sea-bottom, and down to a depth of 2300 fathoms they remain an 
essential constituent of the chalk-like deep-sea ooze. This is a finely divided 
agglomeration of decomposed calcareous substances, such as the shells of 

Fic. 10. 
