PROTOZOA 



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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. YIT. Helioioa. 1. Actinophryg sol, Ehrb. ; x 800. a. food-particle 

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

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

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

 protoplasm. 2. Clathrulina elegant, Cienk. ; x 200. 3. Beter- 



ophryi marina, H. and L. x 660. a, nucleus: *, clearer protoplasm 

 surrounding the nucleus ; t, the peculiar felted envelope. 4. Saplii- 



diophriis pattida, F. E. Schultze ; x 430. a, food-particle ; b, the nucleus ; 

 e, contractile vacuole ; d, 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. Acanthoeystii turfatea, Carter ; 



x 240. a, probably the central nucleus ; 6, clear protoplasm around the 

 nucleus ; c, more superficial protoplasm with vacuoles 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. 6. Bi-flagellate "flagellnla" of 



Acanthncytlit acultaia. a, nucleus. 7. Ditto of Clathrulina elegant, 



a, nucleus. 8. Astrodiseulus ruber, Greeff; x 320. a, red-coloured 



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



CLASS V. HELIOZOA. Haeckel, 1866. 



Characters. Gymnomyxa in which the dominating amceba phase 

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



numerous isolated filamentous pseudopodia which exhibit very little 

 movement or change of 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 vacuoles and 

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

 sphserium). Skeletal products may or may not be present Flagel- 

 lulae 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. 



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FIG. YITI. Heliozoa. 1. Aelinoiphierium Eidihornii, Ehr. : X 200. a, 

 nuclei ; fr, deeper protoplasm with smaller vacuoles and numerous nuclei ; 



c, contractile vacuoles ; d, peripheral protoplasm with larger vacuoles. 

 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 ectosarc); e, pseudopodia showing the 

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

 particle in a food-vacnole. 3, 4. Nuclei of Actinosphaerium in the 

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

 nucleus of Actinosphorium. showing fibrillation, and in 7 and 8 formation 

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

 Cyst-phase of Actinofphterium Eifhhoinii, showing the protoplasm 

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

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

 tht spore. 



