266 PHYSIOGRAPHY. [chap. 



largest, while the others are of intermediate dimensions, 

 disposed around a common centre, and adherent together. 

 Each chamber has an opening in the face which is turned 

 towards the centre; and, in the living state, all the chambers 

 arefiUed with a protoplasmic substance, which spreads over 

 the surfaces of the chambers, and sends out long radiating 

 contractile threads. The walls of the chambers are hard 

 and brittle, from the large quantity of carl)onate of lime 

 which they contain ; and, in the smaller chambers, they are 

 very thin and quite transparent. In the larger, they become 

 thick, and the outer part of their substance acquires a 

 prismatic structure. In specimens taken from the sea with 

 great care, the outer surfaces of the chambers are beset with 

 long slender calcareous processes, like threads of glass ; but 

 these very readily break off. 



The bodies thus described are animals of a very simple 

 character, known as Globigetina bulloides, belonging to 

 the group which has been named the Foraminifei-a} in 

 consequence of the numerous perforations usually visible in 

 their hard parts. It has been a question whether the 

 Globigerhtce live and die at the bottom of the sea, where 

 their skeletons are found ; or, whether they live at the 

 surface, and the shells in the ooze are therefore merely the 

 skeletons of those v/hich have died at the surface, and 

 have thence fallen to the bottom. The investigations of 

 the Challenger have now placed it beyond doubt that, 

 whether any of them live at the bottom or not, they cer- 

 tainly swarm in prodigious numbers at, and a few fathoms 

 below, the surface. They were taken by the tow-net, in 

 all latitudes, over an area extending for between 50° and 60° 

 on both sides of the equator ; and though they abounded 

 most in warm and temperate climates, they were not entirely 

 1 Foraminifera, Lat. foratnai, an aperture ; zxidfero, I carry. 



