337 



sandy and gravelly bottoms are not generally inhabited by 

 these animals, though their de id shells are, not uncommon 

 in the sands along our beaches; while along some shores 

 they are so abundant as to constitute the greater portion, 

 if not the whole, of the deposit.* The vertical range of the 

 benthonic Foraminifera is very great, species sometimes 

 passing through a range of several thousand fathoms. In 

 such cases there is often a change in the size or thickness of 

 the shell with the change in depth. Although the planktonic 

 Foraminifera comprise so few species, the number of their 

 individuals is enormous. From their shells the Globigerina 

 oozes form in deep water, where no sediment is carried ; but 

 it is evident that in a region where the land is reduced to 

 near base level, so that little or no sediment is carried into 

 the sea, pure accumulations tiff such shells will occur near 

 shore, thus forming a foraminiieral ooze in shallow water. 

 But not only planktonic shells but the benthonic species as 

 well would form a pure accumulation of foraminiferal 

 shells, as has been the ease in the ehalk, in which the plank- 

 tonic species are practically wanting. ( Walther, '97, p. 215.) 

 Reproduction of the Foraminifera is carried on by fission, 

 budding, and spore forma tin;;. In the first two cases, the 

 resulting part and the buds have the characteristics of the 

 parent, except its size, and ;i; >re are no special structures 

 which serve fo'r ^M -"greater 1 •''distribution of the species. 

 When sporCs" J %Te if fb f rmed, th'e# Way' %e provided with a 

 fla'gelluin. #l^bP%Hg%i^8tegiaS ¥>&ss through a mero-plank- 

 ^biiic sta^e. 'itudrrtaifc 



While the geogi^rical distention of the benthonic spe- 

 cies 'is' ver'f restricted, and influenced by the facies of the sea 

 bottom, the geographical distribution of the pelagic species 

 is 3 "prevented from being world wide' dnlf-by 'the changes in 

 tne [[ ^en1per v atMe" ; 0f the war-r and by the ocean currents. 

 Tfee 11 pelagic species are ex trem'etf 'abundant in tropical 

 regions, and ; thei f rshells fofiA 1 v:,si accumulations on the sea 



*&' 



~ 



■ -3 '^ln TJivml 3fl t io atoof le i ill ■t o .^T-tb i" ~t] . 



*'Dana states, that in the great barrier-reef region the shells of Orbitolites are so 

 abiuulairt ittyat [fe-f f^rttieforseen^n j^soui^tpiaces^/iBfaKp #ft /M r#}<? le 9W4 o£ tiie 

 beaches, both of the coraT islets' and of the neighboring Australian snore. 



