HELIOZOA. 



187 



ing 



1. IinjH'i-fiiratn. With membranous or calcareous shell, which is without fine 

 purrs, hut possesses, in one place, an opening, either simple or sieve-like, through 

 which the p-mdupodia project. To these belong the GromitJt/; with a mem- 

 branous chitinous shell : Gi'umi/i in'ifoniiix Duj.. and Mil'mlnlfr. with a 

 poroellanous shell : Comuspira planorbis M. Sch.. Milioln ryrloxfinit/i. M. Sch., 

 from the Miliolite chalk. 



2. Perfui'ittti. 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 Luijcnida- have a hard shell, with a large opening surrounded by a 

 toothed lip : Ln/jcna culf/arix Williamson. 



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

 pores, and a simple slit-like open- 

 Orln/liitii intirrrxit D'Orb.. 

 'nni IniUnnli'x D'Orb.. 

 Rotnlln. D'Orb., Tt-.rtnl>-hi. 

 D'Orb. 



The greatest size is attained 

 by the -Y>/niii(fht/rI(e. which 

 possess a firm shell and an in- 

 ternal skeleton, which last is 

 pierced by a complicated canal 

 system : Polystomella Lam.. 

 Nwrnmulvna D'Orb. 



Order 2. HELIOZOA. ' 



Fresh-water lihizopods 

 usually tvit/t 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 (ClatJirulinci), 

 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 Clathrullna." Archie, fur miJtmsl:. Anatinnir, 

 Tom III., 18t;7. R. Greeff, "Ueber Kadiolarien und radiolariena'lmliche 

 Rhizopoden des stissen \Vassers." Tom V. & XT. R. Hertwig und Lesser. 

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

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



FIG. 128. Young Actinosphmrium, still witli a 

 single nucleus (after F. E. Schultze). -A', Nucleus. 



