20 PROTOZOA—RHIZOPODA 
CLASS I 
tests consist of minute grains of sand, often intermingled with particles of 
lime and other foreign matter, the particles being held together by a silicious 
or argillaceous cement. The tests are unilocular or multilocular, occasionally 
attain considerable size, and are either imperforate (Fig. 5, 4), or, in addition 
to the either simple or sieve-like principa] apertures, are punctured by 

Fre. 5, 
A, Section through an imperforate arenaceous 
test, highly magnified (Haplophragmium irrequlare, 
Roem.) £, Section through a perforate arenaceous 
test showing coarse tubuli, highly magnified (Ple- 
canium gibbosum, d'Orb.) 

A, Section of vitreous perforate test with fine 
tubuli (Nodosaria rapa, d’Orb.) B, Portion of 
periphery, and section of a vitreous perforate test 
with coarse tubules less closely set together 
(Globigerina conglomerata, Schwager). 
tubules, through which the pseudopodia are emitted (Fig. 5, B). Caleareous 
tests are also sometimes (Miliolidae, Teatularidae) encrusted with agglutinated, 
compactly cemented sandy particles, and hence consist of an interior caleare- 
ous, and an exterior sandy-silicious layer (Fig. 6). The greater number of 

Fic. § Calcarina calcitrapoides, 
Climacammina textulariformis, Lam. Vitreous perforate 
Moller, sp. Perforate caleareous Operculina complanata, Bast. Miocene; Bor- test with spur-like sup- 
test invested with arenaceous deaux. «a, natural size; 6, median longitudinal plemental skeleton tra- 
envelope. 29/; (after Moller). section ; c, transverse section, greatly enlarged. versed by canals. 
Foraminifera, however, secrete tests composed of carbonate of lime, which 
may be either porcellaneous and imperforate, or vitreous and perforate in 
structure. In the first class (Jmperforata) the shell is homogeneous, and 
appears in reflected light as an opaque mass (Fig. 4); in the second (Perforata) 
it is lustrous, transparent, and perforated by numerous fine tubules which 
pass through the walls radially. These tubules, which are visible on the peri- 
