FORA MINI PER A . 139 



The shells of these foraminifera, though so minute that 

 3,800,000 have been counted in an ounce of sand from the 

 Antilles, are divided, like those of the nautilus, into chambers 

 connected by minute openings, from which they take their 

 name.* The shells of some species are also perforated with 

 innumerable tiny holes through which the inhabitant pro- 

 trudes hair-like filaments of jelly. Though a few are found 



Fig. 28. FORAMINIFERAL SHELLS. 



alive in the ooze, that is not their natural home, for 

 they live on the surface of the ocean, and if they are as 

 numerous to the depth of 100 fathoms as they are in 

 the track of the tow-net, every square mile of the ocean 

 must contain sixteen tons of carbonate of lime, in the form 

 of calcareous shells. These, as the inhabitants die, fall down 

 in a constant rain, and accumulate on the ocean-bed. In 

 some cases, half the sand on the sea-shore is made up of 

 them, and they have had a large share also in the formation 

 of coral islands. 



They abound to such an extent in the limestone used for 



* Latin, foramen, a hole. 



