10 PALEONTOLOGY 



The several segments or jelly-filled chambers are essentially 



repetitions of each other ; and there is no proof that the inner 

 and earlier segments derive their nourishment from the outer 

 and last-formed one. A Foraminifer may therefore be regarded 

 either as a series of individuals, organically united, or as a 

 single aggregate being, compounded according to the law of 

 vegetative repetition. 



The minute chambered shells of Foraminifcra enter 

 largely into the composition of all the sedimentary strata, and 

 are so abundant in many common and familiar materials, like 

 the chalk, as to justify the expression of Buffon, that the very 

 dust had been alive. The deep-sea soundings of the Atlantic 

 Telegraph Company have shown that the bed of that great 

 ocean, at a depth approaching, or even exceeding, two miles. 

 is composed of little else than the calcareous shells of a 

 Glohigcrina and a few other Iihizopods, with the silicious 

 shields of the allied Polycijstinccv. The composition of the 

 ehalk is extremely similar : when the finer portion, amounting 

 to half or even less, has been washed away, the remaining 

 sediment consists almost entirely of foraminated shells, some 

 perfect, others in various stages of disintegration They have 

 also been found in other marine formations, which are soft 

 enough to be washed, down to the Lower Silurian ; and in the 

 hard limestones and marbles they can be detected in polished 

 sections, and in thin slices laid on glass. The greater part of 

 these shells are microscopic, but some of the large extinct 

 Foraminifcra, called, from resembling a piece of money, 

 " Numnmlites," are two inches in diameter. 



The generic divisions in use for these shells were mostly 

 invented by M. d'Orbigny, but on artificial grounds, viz., 

 exclusively upon the plan of growth, or mode of increase in 

 the number of chambers. The structure and anamorphoses 

 of these complex atoms have been recently investigated by 

 Messrs. Williamson and Carpenter, and especially by Mr. 



