118 WORMS, MOSS-POLYPS, SPONGES, ETC. 
line, or, what is more usually the case, in one or 
more circles around the initial sphere. A com- 
plex arrangement of chambers may thus be built 
up, especially if the system of development has 
proceeded along more than a single plane. Of 
such a complex character is our little Rotalia of 
the ocean sands, the different chambers in the shell 
of which can be clearly traced out with the aid of 
the microscope. 
The Foraminifera lead an apparently very inde- 
pendent life on the ocean wave, tossed hither and 
thither among the seething waters: their home is 
not merely the surface, but extends to the gloomier 
shades of the abyss. At the bottom of the sea the 
shells of the dead animals accumulate in prodigious 
numbers, forming there a deep white or gray mud 
known as the ‘ Atlantic ooze.’ It is this same sub- 
stance compacted which constitutes true chalk, and 
likewise much of the hard limestone and marble 
which we see everywhere about us. At one time 
the areas where we now find chalk and marble 
were beneath the sea, but through movements of 
the earth’s crust of one kind or another they have 
been brought to their present inland positions. 
The so-called ‘ greensands’ or ‘ marls’ of New Jer- 
sey are largely a foraminiferal composition, the 
little green pellets of the mineral glauconite, 
which give the distinctive appearance to the sand, 
representing principally the fillings or casts of an 
endless number of foraminiferal shells, from which 
the lime has been removed through solution. 
