HELIOZOA. 



187 



1. Imperfurata. 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 Gromidce, with a mem- 

 branous chitinous shell : Gromia oviformis Duj., and Miliolidfe, with a 

 porcellanous shell : Cornuspira planorbis 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 LagenidcB have a hard shell, with a large opening surrounded by a 

 toothed lip : Lagena vulgaris Williamson. 



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

 pores, and a simple slit-like open- 

 ing : Orbulina, universa D'Orb., 

 Gloligevina bulloides D'Orb., 

 Rotalia D'Orb. , Textularia 

 D'Orb. 



The greatest size is attained 

 by the Nummulinida, which 

 possess a firm shell and an in- 

 ternal skeleton, which last is 

 pierced by a complicated canal 



system : Polystomella 

 Nummulina D'Orb. 



Lam. 



\ 



Order 2. HELIOZOA.* 



Fresh-water Rhizopods 

 usually with pulsating vacu- 

 ole, and one or more nuclei. 

 A radial silicious skeleton 

 sometimes present. 



The sarcode 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." Arcliiv. fur mihrosk. Anatomie, 

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

 Rhizopoden des siissen Wassers." Tom V. & XT. R. Hertwig und Lesser, 

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

 X., 1874. Also Aroher and F. E. Schultze, etc. 



123. Young ActinofpTicenum, stiH with a 

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



