IIELIOZOA. 



1S7 



1. Imperforata. With membranous or calcareous shell, which is without fine 

 pores, but possesses, in one place, an opening, either simple or sieve-like, through 

 which the pseudopodia project. To these belong the GromidfP, with a mem- 

 branous chitinous shell : Gromia or If or mis Duj., and Miliolidtf, with a 

 porcellanous shell : Cornuspira planorl>is M. Sch., Miliola cyclostoma M. Sch., 

 from the Miliolite chalk. 



2. Perforata. The shell, which is usually calcareous, is invariably pierced with 

 innumerable fine pores as well as by one larger opening, and has complicated 

 passages in the partition walls of its chambers. 



The La-geniJce have a hard shell, with a large opening surrounded by a 

 toothed lip : Lagena vulgar is Williamson. 



The Globigerinidce on the contrary have a hyaline shell pierced by large 

 pores, and a simple slit-like open- 

 ing : Orlulina universa D'Orb., 

 Ghibif/crina bulloides D'Orb., 

 Ilutnliti D'Orb., Textularia 

 D'Orb. 



The greatest size is attained 

 by the JVumiiiU/iifl(p, which 

 possess a firm shell and an in- 

 ternal skeleton, which last is 

 pierced by a complicated canal 

 system : Polystomella Lam., 

 Niiinmulina D'Orb. 



Order 2. HELIOZOA.* 



Fresh-water Rhizopods 

 usually with pulsating vacu- 

 ole, and one or more nuclei. 

 A radial silicious skeleton 

 sometimes present. 



The sareode body sends 

 out in all directions tough 

 radiating pseudopodia (fig. 

 128). When a skeleton is 

 secreted, it consists either of 

 radially arranged silicious 



spines (Acanthocystis) or of latticed silicious shells (Clathrulina), 

 and so closely resembles the skeleton -of the Radiolaria that the 

 Heliozoa have been actually described as fresh-water Radiolaria, 



They differ from the Radiolaria in the absence of the complicated 



* L. Cienkowski, " Ueber Clathrulina" Arcliio. fur mikrosb. Anatomic, 

 Tom III., 1867. R. Greeff, " Ueber Radiolarien und radiolarienahnliche 

 Ehizopoclen des siissen Wassers." Tom V. & XT. R. Hertwig urid Lesser, 

 " Uber Rhizopoden und denselben nahe stehende Organismen." Suppl. Tom 

 X., 1871. Also Arohcr and F. E. Schultze, etc. 



Pro. 12S. Young ActinospJitErium, stil-1 with ;i, 

 single nucleus (aftei F. E. Sehultze). N, Nucleus. 



