RIIIZOPODA. 27 



of varied forms, more or less spherical, perforated for the 

 protrusion of the pseudopodia, with often spicules or points 

 radiating from the shell. They reproduce apparently hy 

 self -division of the interior, resulting in a swarm of monad- 

 like young. The Heliozoa are represented hy the fresh- 

 water Actinoplirys sol, which is round, with numerous stiff 

 pseudopodia radiating in all directions from the body, and 

 by Actinosphaerium (Fig. 16). The true marine Radiolaria 

 are represented by Collosplmra spinosa Cienkowski (Fig. 15). 

 It possesses a perforated shell beset with small spines, which 

 encloses a capsule with a protoplasmic wall. In the capsule- 

 stage (A) it often divides by fission into two halves. After- 

 ward the older capsule divides into a number of little round 

 bodies, which develop two lashes as in (7. 



CLASS II. RHIZOPODA. 



Unicellular organisms consisting of protoplasm, with an outer clear, 

 cortical, and an inner granular mass containing one or more nuclei, and 

 one or more contractile vacuoles ; moving by means of pseudopodia, and 

 either naked or secreting a one or many -chambered sliell ; reproducing by 

 self -division, or by the production of several or many amoeboid or monad- 



Order. 1. Foraminifera. One-celled Rhizopods with one or many nuclei 

 and contractile vacuoles, secreting chambered calcareous or 

 horny (chitinous ?), rarely arenaceous, shells. (Amoeba, 

 Globigerina, Nummulina.) 



Order 2. Radiolaria. Rhizopods with pointed, branched, usually anas- 

 tomosing and granular pseudopodia. The body contains 

 either numerous small heterogeneous nuclei, or a single 

 larger, highly differentiated vesicular nucleus. The pro- 

 toplasm of the body is further separated into a peripheral 

 non-nucleated and a central nucleated portion by a mem- 

 branous capsule with porous walls. Reproduction occurs 

 by the breaking up of the body into monad-like embryos, 

 with one or sometimes two locomotive lashes (flagella). 

 There are two divisions : (1) Heliozoa (Actinophrys, Actino- 

 sphaerium), and (2) Radiolaria (or Cytophora), having as rep- 

 resentatives Acanthometra, Collozoiim, Sphaerozoum, and 

 Collosphacra. 



