16 



PROTOZOA 



ORDER 1. APHROTHORACA, Hcrtwig (56). 



Characters. Heliozoa devoid of a spicular or gelatinous envelope, 

 excepting in some a temporary membranous cyst. 



Genera. Nuclearia, Cienk. (37) (many nuclei ; many contractile 

 vacuoles ; body not permanently spherical, but amoeboid) ; Actin- 

 ophrys, Ehr. (Fig. VII. 1 ; body spherical ; pseudopodia with an 

 axial skeletal filament ; central nucleus ; one large contractile 

 vaeuole; often forming colonies ; A. sol, the Suu -animalcule); 

 Actinosphserium, Stein (Fig. VIII. ; spherical body ; pseudopodia 

 with axial filament ; nuclei very numerous ; contractile vacuoles 2 

 to 14) ; Actinolophus, F. E. Schulze (stalked). 



ORDEK 2. CHLAMYDOPHORA, Archer (57). 



Characters. Heliozoa with a soft jelly-like or felted fibrous 

 envelope. 



Genera. Heterophrys, Archer (Fie. VII. 3); Sphamastrum, 

 Greeff; Astrodisculus, Greeff(Fig. VII. 8). 



ORDER 3. CHALAROTHORACA, Hertw. and Lesser (58). 



Characters. Heliozoa with a loose envelope consisting of isolated 

 siliceous spicules. 



Genera. Raphidiophrys, Archer (Fig. VII. 4 ; skeleton in the 

 form of numerous slightly curved spicules placed tangentially in 

 the superficial protoplasm) ; Pompholyxophrys, Archer ; Pinacocystis 

 H. and L. ; Pinaciophora, Greeff ; Acanthocystis, Carter (skeleton 

 in the form of radially disposed siliceous needles ; encysted con- 

 dition observed, and flagellula young, Fig. VII. 6) ; Wagnerella, 

 Meresch. 



ORDER 4. DESMOTHORACA, Hertw. and Less. 



Characters. Heliozoa with a skeletal envelope in the form of a 

 spherical or nearly spherical shell of silica preforated by numerous 

 large holes. 



Genera. Orbulinella, Entz (without a stalk) ; Clathrulina, 

 Cienk. (with a stalk, Fig. VII. 2). 



Further remarks on the Heliozoa. The Sun-animalcules, Actino- 

 phrys and ActinosphEerium, were the only known members of this 



froup when Carter discovered in 1863 Acanthocystis. Our further 

 nowledge of them is chiefly due to Archer of Dublin, who dis- 

 covered the most important forms, and figured them in the Quart. 

 Jour. Micr. Sci. in 1867. 



Some of the Proteomyxa (e.g., Vampyrella) exhibit " heliozoon- 

 like " or " actinophryd " forms, but are separated from the true 

 Heliozoa by the fact that their radiant pseudopodia are not main- 

 tained for long in the stiff isolated condition characteristic of this 

 group. It is questionable whether Nuclearia should not be relegated 

 to the Proteomyxa on account of the mobility of its body, which in 

 all other Heliozoa has a constant spherical form. 



Actinophrys sol is often seen to form groups or colonies (by 

 fission), and so also is Raphidiophrys. It is probable from the 

 little that is known that reproduction takes place not only by 

 simple fission but by multiple fission, producing flagellate spores 

 which may or may not be preceded by encystment. Only Clath- 

 rulina, Acanthocystis, Actinosphserium, and Actinophrys have 

 been observed in the encysted state, and only the first two have 

 been credited with the production of flagellated young. The two 

 latter genera form covered spores within their cysts, those of Actino- 

 sphaerium being remarkable for their siliceous coats (Fig. VIII. 

 14), but their further development has not been seen. 



CLASS VI. RETICULAEIA, Carpenter, 1862. 

 (Foraminifera, Auct., Thalamophora, Hertwig). 



Characters. Gymnomyxa in which the dominating amoeba- 

 phase, often of great size (an inch in diameter), has an irregular 

 form, and a tendency to throw out great trunks of branching and 

 often anastomosing filamentous pseudopodia, and an equally strong 

 tendency to form a shell of secreted membrane or secreted lime or of 

 agglutinated sand particles (only in one genus of secreted silex) into 

 which the protoplasm (not in all ?) can be drawn and out of and 

 over which it usually streams in widely spreading lobes and 

 branches. One nucleus is present, or there arc many. A contrac- 

 tile vaeuole is sometimes, but not as a rule, present (or at any rate 

 not described). Reproduction is by fission and (as in some other 

 Protozoa) by the formation of peculiar bud-spores which remain 

 for a time after their formation embedded in the parental proto- 

 plasm. No multiple breaking up into spores after or independent 

 of the formation of a cyst is known. Marine and freshwater. 



The Reticularia are divisible into several orders. The marked 

 peculiarity of the shell structure in certain of these orders is only 

 fitly emphasized by grouping them together as a sub-class Per- 

 forata, in contrast to which the remaining orders stand as a 

 sub-class Imperforata. The distinction, however, is not an ab- 

 solute one, for a few of the Lituolidea are perforate, that is, are 

 sandy isomorphs of perforate genera such as Globigerina and 

 Rotalia. 



Fro. IX. Gromiidea (Reticularia membranosa). 1. 

 Archeri, Barker, a, nucleus ; &, contractile vacuoles ; c, the yellow oil-like 

 body. Moor pools, Ireland. 2. Gromia oviformis, Duj. a, the 



numerous nuclei ; near these the elongated bodies represent ingested 

 Diatoms. Freshwater. 3. Shepheardella tieniifonnis, Siddall (Quart. 

 Jour. Micr. Sci., 1880); X 30 diameters. Marine. The protoplasm is 

 retracted at both ends into the tubular case, a, nucleus. 5. Shep- 



heardella tseniiformis ; x 15 ; with pseudopodia fully expanded. 

 6-10. Varying appearance of the nucleus as it is carried along in the 

 streaming protoplasm within the tube. 11. Amphitrema Wrightianum, 

 Archer, showing membranous shell encrusted with foreign particles. 

 Moor pools, Ireland. 12. Diaphorophodon mobile, Archer, a, nucleus. 



Moor pools, Ireland. 



SUB-CLASS A. Imperforata. 



Characters. Shell-substance not perforated by numerous aper- 

 tures through which the protoplasm can issue, but provided with 

 only one or two large apertures, or in branched forms with a few 

 such apertures. 



ORDER 1. GROMIIDEA, Brady. 



Characters. Shell or test membranous, in the form of a simple 

 sac with a pseudopodial aperture either at one extremity or at both. 

 Pseudopodia thread-like, long, branching, reticulated. Marine and 

 freshwater. 



Fam. 1. MONOSTOMINA, with a single aperture to the shell. 



