44 . THE EOT ALINE GENUS. PART in. 



septa, or partitions ; and it is through the pores of the 

 last septum that the pseudopodia of the animal have 

 access to the water to provide for the growth of the 

 spire, for the punctures on the surface are merely the 

 terminations of some of the branching canals. On ap- 

 proaching the surface the canals become crowded to- 

 gether in some parts, leaving columns of the shelly 

 skeleton unoccupied which either appear as tubercles 

 on the surface, or, if they do not rise so high, form 

 circular spots surrounded by punctations which are 

 the apertures of the canals. 



The Rotaline series of the Globigerina family is one 

 of the most numerous and varied of the whole class of 

 Foraminifera ; but varied as their forms are, they all bear 

 the characteristic marks which distinguish their order, 

 with this essential difference, that in the genus Globi- 

 gerina each chamber of the spire has a communication 

 with the central vestibule by a crescent-shaped aperture, 

 while in the Rotalinae each chamber only communicates 

 by a crescentic aperture with that which precedes and 

 follows it. 



In the Rotaline group the internal organization rises 

 successively from the simple porous partition between 

 the chambers, to the double partition with the radiating 

 passages, and from the latter to the double partitions, 

 intermediate skeleton, and complicated system of canals. 

 To these changes the structure of the compound animal 

 necessarily corresponds, for it may be presumed that 

 not only the chambers but all the passages and canals 

 in the interior of the shell are either permanently or 

 occasionally filled with its sarcode body. 



However, it is in the Nummuline family that the 

 Foraminifera attain the highest organization of which 

 they are capable. This family surpasses all the 

 Vitreous tribe in the density and toughness of the shell, 

 the fineness of its tubuli, and in the high organization 



