FORAMINIFERA. 



(14.) When a Rhizopod, having all its filaments thus extended, 

 wishes to advance in any given direction, those threads which are 

 directed in front become elongated, and those placed behind, on the 

 contrary, are drawn forward, while the intermediate move so as to 

 accommodate themselves to each change of position, thus evidently 

 exhibiting a consentaneity of action. 



(15.) Internally these creatures present no traces of any special nutri- 

 tive apparatus ; neither are there any organs appropriated to reproduction, 

 their multiplication being apparently accomplished either by gemmation 

 or by simple division, as any portion of the mass separated from the rest 

 seems capable of living and of forming a new centre of organization. 



(16.) The delicate body of Gromia, above described, is unprovided 

 with anything like a shell; but there are many races presenting an 

 organization in every way analogous (such as the Hiliolce, the Cristel- 

 larice, the Vorticialce, and others), that possess the power of secreting 

 shells of very exquisite texture, many of which form extremely beautiful 

 objects when examined under the microscope. 



(17.) The FOKAMINIFERA constitute a very curious and remarkable 



group, important from the immense num- 

 bers in which they occur in a fossil state, 

 and interesting from the peculiarities of 

 structure whereby they are distinguished. 

 The shells of these singular organisms 

 (fig. 2) are divided into distinct com- 

 partments*, so as almost exactly to re- 

 semble in their form the camerated shells 

 of the Nautili, Ammonites, and other 

 highly-organized mollusca. Examined, 

 however, in a living state, they are 

 found to belong to animals of a very 

 different type, as remarkable for the 

 simplicity of their organization as for 

 their elegance and delicacy. The shell, 

 as represented in the figure, consists of 

 numerous chambers divided from each 

 other by calcareous septa, and perfo- 

 rated by innumerable minute orifices, 

 or foramina, from which circumstance 

 is derived the characteristic name. In- 

 ternally these chambers are entirely filled 

 with a homogeneous, transparent, glairy 



Fig. 2. 



1. Nonionina, exhibiting pseudcpodia 



protruded through the foramina in 

 substance, which, being Soft and diffluent, 2 . The Rafter" th'eloWon of the 



like the arms of Gromia described above, she11 in weak acid - 



* Whence the group has also received the name of POLYTHALAMIA, i. e. many- 

 chambered. 



