554 
the lo west animals. 
Order Fohaminifera. 
W 
\ 
\! 
/ h 
I f/y 
■’"Ms/ r 
js, 
/ 
AWIfVVJV/- 
N '»-, 'V>. . ^■^ C - r *SA J »^ 
\ J% 
_/ r 
If shelly sea-sand be looked over with a lens, there will often be seen tiny 
shells no bigger than the grains of sand amongst which they lie. The specimen 
illustrated on p. 558, and whose shell is about one - twentieth of an inch in 
diameter, was originally named the 
spiral nautilus, with crenated joints. 
Another kind (Miliolina) occurs in 
the shape of porcelain-like oval shells, 
one-twentieth of an inch in length, 
with about five visible segments, 
arranged somewhat like a string of 
sausages wound round each other not 
O 
quite in the same plane. Foraminifera 
are rhizopods whose simple sarcode- 
bodies emit slender branching pseu¬ 
dopods, and which form a shell of 
membrane, of foreign particles of 
sand, etc., of carbonate of lime, or, in 
rare instances, of silica. The order is 
divided into two groups, the Imper- 
forata and the Perforata; in the former 
of which the shell possesses only one 
or a few comparatively large aper¬ 
tures, whereas in the latter, in addition 
to its main opening, the shell has its 
walls perforated all over with small 
pores through which pseudopods can 
be emitted. 
The Imperforata form shells of 
membrane, agglutinated particles of 
sand, mud, sponge-spicules, etc., or of 
carbonate of lime; the vast majority 
of the Perforata form shells of the 
last-named material. The imperforate 
shells of carbonate of lime often resemble milk-white porcelain; whereas the per¬ 
forate shells, especially in early stages, have a glassy appearance. 
Gromia is found both in fresh and brackish water and in the sea in 
the form of minute, oval, egg-shaped bodies about one-twentieth of an inch 
in length, fixed on tufts of corallines, or loose in the sand and mud. At first 
there appears to be nothing remarkable about the tiny oval mass resembling 
the egg of a zoophyte; but presently from the opening at one end of the 
membranous sac or shell granular threads of sarcode creep out and become 
fixed on the glass slide; slender trunks of sarcode extend themselves, and divide 
into finer and finer branches, which reunite to form a network of streaming 
granular filaments ever changing in form, and which may extend to six or eight 
JhM 
/AU 
■i w 
/ i \h\ 
pa 
'Hv 
) 
egg-shaped gromia, Gromia oviformis (magnified 
600 diameters). 
