58 MANUAL OF ZOOLOGY. 



Actinophrys will be placed amongst the Amozbea, to which its 

 alliance appears to be more decided. 



The order Radiolaria may be defined as comprising those 

 Rhizopods which possess a siliceous test or siliceous spicules, and 

 are provided with pseudopodia which stand out like radiating fila- 

 ments, and occasionally run into one another. 



I. FAMILY ACANTHOMETRINA. The Acanthometrce (fig. 6, a) 

 are all minute, and are found floating near the surface in the 

 open ocean, sometimes in great numbers. They consist of 

 sarcode-bodies which are supported by a framework of radiat- 

 ing siliceous spines, the extremities of which usually project 

 considerably beyond the body. The substance of the body 

 admits of division into an outer membranous layer, or " ecto- 

 sarc," and an internal granular layer, or " endosarc." The 

 siliceous spines are hollow, being grooved at the base by a 

 gutter, which is continued further up the spine by a canal ter- 

 minating at the apex of the spine by a distinct aperture. The 

 spines, in consequence of this structure, are able to serve for the 

 transmission of the pseudopodia, which gain the exterior by 

 running through the canals and escaping at their apices. Many 

 of the pseudopodia, however, do not occupy the canals of the 

 spines. 



Fig. 6. a Acanthometra lanceolata ; b Haliomma kexacantkum, one of the 

 Polycystiiia, showing the radiating pseudopodia. (After Mttller.) 



II. FAM. POLYCYSTINA. The members of this family are 

 closely related to the Foraminifera, differing from them chiefly 

 in the fact that their shells are composed of flint instead of 

 carbonate of lime, as in most of the latter. They possess a 

 body of sarcode, which is enclosed in a foraminated siliceous 

 shell, which is often furnished with spine-like processes, and is 

 usually of great beauty (fig. 6, b). The sarcodic substance of 

 the body is olive-brown in colour with yellow globules, and 



