52 ZOOLOGY SECT. 



ORDER 2. FILOSA. 



The order Filosa comprises a small number of Rhizopods having 

 affinities with some of the Lobosa on the one hand and with the 

 Foraminifera on the other. The pseudopodia are very fine and 

 thread-like, and become branched towards the ends : unlike those 

 of the Foraminifera, they do not coalesce with one another except 

 at or near the proximal ends and do not form networks. There is 

 no clear exoplasmic layer. The best known of the Filosa 

 Euglypha has a flask-shaped test composed of close-fitting hexa- 

 gonal siliceous plate* 



o- vac 



B 



FIG. 35. Chlamydophrys stercorea. A, single zooid ; -B, formation of colony ; c. vac. 

 contractile vacuole ; /. food particles ; nu. nucleus ; sh. shell. (From Biitschli's Protozoa, 

 after Cienkowsky.) 



ORDER 3. FORAMINIFERA. 



General Structure. The members of this order differ from 

 the Lobosa in the fact that their pseudopods are long and delicate 

 and unite to form networks ; moreover, with few exceptions, they 

 agree with Arcella and its allies in possessing a shell. In the 

 majority of cases this shell is formed of calcium carbonate. 



One of the simplest members of the group is Microgromia (Fig. 

 34). It consists of a protoplasmic body (B), with a single nucleus 

 (nu.) and contractile vacuole (c. vac.), enclosed in a chitinoid cell- 

 wall or shell (sh.) with an aperture at one end through which the 

 protoplasm protrudes and is produced into delicate radiating 

 pseudopods. The animal multiplies by binary fission, and the 

 individuals or zooids thus produced remain united in larger or 

 smaller clusters, or cell-colonies (A). Sometimes the cell-body of a 

 zooid divides and one of the daughter-cells creeps out of the cell- 

 wall (C), and, after moving about for a time like an Amoeba, draws 

 in its pseudopods, assumes an oval form, and sends out two 

 flagella by means of which it is propelled through the water (D). 



