337 



sandy and gravelly bottoms are not generally inhabited by 

 these animals, though their dead 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 

 benthonie 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 tlieir 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 of such shells will occur near 

 shore, thus forming a foraminiferal ooze in shallow Avater. 

 But not onh' planktonic shells but the benthonie s]iecies as 

 well would form a pure accumulation of foraminiferal 

 shells, as has been the case in the chalk, in which the plank- 

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

 Eeproduction of the Foraminifera is carried on by fission, 

 budding, and spore formation. In the first two cases, the 

 resulting part and the buds have the charactei-istics of the 

 parent, except its size, and there are no special structures 

 which serve for tlie greatei' distribution of the species. 

 When spores are formed, these may be provided with a 

 flagellum, when the organisms pass through a mero-plank- 

 tonic stage. 



While the geographical distribution of the benthonie spe- 

 cies is very restricted, and influenced by the facies of the sea 

 bottom, the geographical distribution of the pelagic species 

 is prevented from being world wide only by the changes in 

 the temperature of the water and liy the ocean currents. 

 The pelagic species are extremely abundant in tropical 

 regions, and their shells form vast accumulations on the sea 



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

 abundant that * * •' they seemed in some places to make up the whole sand of the 

 beaches, both of the coral islets and of the neighboring Australian shore." 



