PROTOZOA: FORAMINIFERA. 73 



Gromia in structure, but forms loose colonies by the root-like 

 union of the pseudopodia of a number of individuals. It lives 

 in fresh water, and reproduces itself by giving exit to amoeboid 

 masses of protoplasm, each of which develops two flagella, 

 thus constituting free locomotive " swarm-spores." Euglypha 

 and Diplophrys are other forms allied to Gromia, the former 

 having an inflexible and sculptured test, while the latter has 

 two oppositely-placed apertures in the shell, in place of a single 

 terminal opening. 



CHALLENGERIDA. In the neighbourhood of Gromia we 

 may, perhaps, place the singular marine Rhizopods which Sir 

 Wyville Thomson has raised to the rank of a distinct order 

 under the name of Challengerida, from the type-genus Challen- 

 geria. This group comprises minute Rhizopods enclosed in a 

 monothalamous test of silica, the form of which varies, being 

 globular, lenticular, flask-shaped, or triangular. The surface 

 of the shell is usually sculptured, often with deeply sunk pits, 

 and there is a single pseudopodial aperture, " usually guarded 

 by a beautifully-formed and frequently highly-ornamented lip " 

 ('The Atlantic/ vol. ii. p. 341). The sarcode in the interior 

 of the test is granular, with one or more nuclei, and with a 

 number of brown or nearly black, compound, granular bodies. 



CLASSIFICATION OF THE FORAMINIFERA. The classification of the 

 Foraminifera has proved a matter of considerable difficulty. The older 

 arrangements were unnatural, as being based wholly on the form of the 

 shell, a point in which the Furaminifera show a most marvellous variability. 

 For this reason the artificial systems proposed by D'Orbigny and Max 

 Schultze have now been generally abandoned, and their place has been 

 taken by the schemes of classification put forward independently and 

 almost simultaneously by Professor Von Reuss upon the Continent, and by 

 Dr Carpenter, Mr Parker, and Professor T. Rupert Jones in this country. 

 Both these arrangements agree in the essential feature that they divide the 

 Foraminifera into two great primary divisions, in accordance with the 

 nature of the shelly investment. In the one division (Imperforata), the 

 test is not perforated by pseudopodial apertures, and it may be either 

 "arenaceous" or " porcellanous. " In the other division the test is per- 

 forated by more or less numerous pseudopodial foramina, and to this 

 division the name of Perforata is applied. The following tables exhibit 

 the arrangements proposed by Carpenter, Parker, and Rupert Jones, on 

 the one hand, and Reuss, on the other hand ; the former being the most 

 natural, and the one most widely adopted : 



CLASSIFICATION OF THE FORAMINIFERA, ACCORDING TO CARPENTER, 

 PARKER, AND RUPERT JONES. 



SUB-ORDER I. IMPERFORATA. Test membranous, calcareous, or 

 arenaceous, not perforated by pseudopodial foramina. 



Family I. Gromida. 

 it 2. Miliolida. 

 M 3. Litnolida, 



