PROTOZOA 



15 



of the network appear to consist of contractile protoplasm, whilst 

 in the latter they are described as firm horny threads exuded by 

 the spindle-cells. Neither form has been re-examined since its 

 discovery ; and it is possible that this apparent difference will be 

 removed by further study. 



FIG. VII. Heliozoa. 1. Aetinophrys sol, Ehrli. ; x SOO. a. food-particle 

 lying in a large food-vacuole ; b, deep-lying finely granular protoplasm ; c, 

 axial filament of a pseudopodium extended inwards to the nucleus; d, the 

 central nucleus ; e, contractile vacuole ; /, superficial much-vacuolated 

 protoplasm. 2. Clathndina clegaiis, Cienk. ; X 200. 3. Hetcr- 



ophrys marina, H. and L. x 660. a, nucleus ; b, clearer protoplasm 

 surrounding the nucleus; c, the peculiar felted envelope. 4. /Vrc//A<'- 



diophrys pallida, F. E. Schultze ; x 430. a, food-particle ; b, the nucleus ; 

 c, contractile vacuole ; it, central granule in which all the axis-filaments of 

 the pseudopodia meet. The tangentially disposed spicules are seen 

 arranged in masses on the surface. 5. Acanthoc'/stis turfacea, Carter; 



X 240. a, probaldy the central nucleus ; b, clear protoplasm around the 

 nucleus ; c, more superficial protoplasm with vaeuoles and chlorophyll 

 corpuscles ; d, coarser siliceous spicules ; e, finer forked siliceous spicules ; 

 /, finely granular layer of protoplasm. The long pseudopodia reaching 

 beyond the spicules are not lettered. C. Hi-flagellate "flagellula" of 



Acunthacystis aculeata. a, nucleus. 7. Ditto of Clathrulina elegans. 



a, nucleus. 8. Astroilisculus ruber, Green* ; x 320. a, red-coloured 



central sphere (? nucleus) ; b, peripheral homogeneous envelope. 



CLASS V. HELIOZOA, Haeckel, 1866. 



Characters. Gymnomyxa in which the dominating amoeba phase 

 has the form of a spherical body from the surface of which radiate 



numerous isolated filamentous pseudopodia which exhibit very little 

 movement <>r change <>( form, except when engaged in the inception 

 of food-particles. The protoplasm of the spherical body is richly 

 vacuolated ; it may exhibit one or more contractile vaeuoles and 

 either a single central nucleus or many nuclei (Nuclearia, Aetino- 

 sphterium). Skeletal products may or may not be present. Flagi-1- 

 lulaj have been observed as the young forms of some species (Acan- 

 thocystis, Clathrulina), but very little has been as yet ascertained 

 as to spore-formation or conjugation in this group, though isolated 

 facts of importance have been observed. Mostly freshwater forms. 



II 



FIG. Till. Heliozoa. 1. AcKnospluerium EicliJiornii, Ehr. ; x 200. a, 

 nuclei ; b, deeper protoplasm with smaller vaeuoles and numerous nuclei ; 



c, contractile vaeuoles ; rf, peripheral protoplasm with larger vaeuoles. 

 2. A portion of the same specimen more highly magnified and seen in 

 optical section, a, nuclei ; b, deeper protoplasm (so-called endosarc); 



d, peripheral protoplasm (so-called eetosarc); e, pseudopodia showing the 

 granular protoplasm streaming over the stitf axial filament ; /, food- 

 particle in a food-vacuole. 3, 4. Nuclei of Actinosphrcrium in the 

 resting condition. 5-13. .Successive stages in the division of a 

 nucleus of Actinosphrcriuni, showing fibrillation, and in 7 and 8 formation 

 of an equatorial plate of cliroinatin substance (after Hertwig). 14. 

 Cyst-phase of Actum-i'ti^'i-hnii BicAAomii, showing the protoplasm 

 divided into twelve chlamyduspores, each of which has a siliceous coat ; 

 a, nucleus of the spore ; g, gelatinous wall of the cyst ; ft, siliceous coat of 

 the spore. 



