SECT. ii. VITREOUS FORAMIN1FERA. 41 



diameter, arranged at pretty regular distances ; but in 

 deep seas the surface of the shell is raised by an external 

 deposit into tubercles or ridges, the orifices of the pores 

 appearing between them. 



Each chamber of the shell is occupied by a reddish- 

 yellow segment of sarcode, from which .pseudopodia 

 are seen to protrude ; and it is supposed* thai v the 

 sarcode body also fills the vestibule, since without 'siich 

 connecting band it is difficult to understand how the 

 segments which occupy the separate chambers can com- 

 municate with each other, or how new segments can be 

 budded off. In the Globigerina the slight cohesion 

 gives reason to believe that the separation of the parts 

 may be a means of reproduction. 



The Rosalina ornata, one of the most beautiful speci- 

 mens of this group, and remarkable for the size of its 

 pores, is represented in fig. 100 with its pseudopodia ex- 

 tended, and coalescing in some parts. 



The shells of the genus Textularia consist of a double 

 series of chambers disposed on each side of an axis, so that 

 they look as if they were mutually interwoven. As the 

 segments for the most part increase gradually in size, 

 the shell is generally triangular, the apex being 

 formed of the first segment, and its base of the two last 

 (H, fig. 97). 



The aperture is always placed in the inner wall of 

 each chamber, close to its junction with the preceding 

 segment on the opposite side. In the compressed shells 

 it is crescent-shaped, but it is semilunar in the less 

 compressed, and may even be gibbous. The shell is 

 hyaline, with large pores not very closely set, though 

 in some varieties they are minute and near to one 

 another. Sometimes the pores open on the surface in 

 deep hexagonal pits. The older shells are frequently 

 incrusted with large coarse particles of sand, and some 

 specimens from deep water are almost covered with fine 



