CLASSIFICA TION OF PROTOZOA. 109 



dealt with." They are simple in structure, often parasitic in habit, and 

 protean in their phases. In some, no central body or nucleus has yet 

 been detected. They occur in fresh water, in the sea, and parasitically. 

 Examples. — Protomyxa, in four phases : — (i) encysted and breaking 

 up into spores, which (2) are briefly active, (3) sink into amoeboid forms, 

 (4) flow together into a composite " Plasmodium. " Vampyrella, para- 

 sitic on fresh- water Algse. Protogenes, the simplest "amceba." Pro- 

 tobathybius, dredged up in masses from the depths. Schizogenes, 

 multiplying by mere breakage. Archerina, with chlorophyll, like a 

 sun-animalcule (Heliozoon). Monobia, dividing into beautiful colonies, 

 illustrating "sociality" at a low level. 



2. Mycetozoa. — Protozoa which live on land and have a furigus- 

 like habit of feeding on decaying vegetable matter. The plasmodial 

 stage in the cycle is predominant. From encysted plasmodia, or parts 

 of them often elaborate in structure, coated spores are produced ; the 

 spores may have a brief flagellate activity and sink down into amoeboid 

 forms, or become at once little amoebje ; the amcebse grow and conse- 

 quently multiply, and after a while collect into the characteristic fused 

 masses or plasmodia. 



Example. — Fuligo or ALthalium septiciim, "flowers of tan" — a 

 large spreading mass found in summer on the bark of the tan yard. 

 This and the other forms are sometimes ranked as plant organisms, but 

 De Bary, whose opinion is authoritative, has given good reasons for 

 keeping them among the Protozoa. It is of course natural that some of 

 these primitive forms shoiUd appear to hesitate between the two paths. 



£. — Predominantly Ammhoid Protozoa — Rhizopoda. 



3. LoBOSA, in which the living matter flows out and in as protean, 

 usually blunt, never interlaced processes. A physical difference between 

 outer and inner portions, one nucleus or more, bubbles of water 

 engulfed along with the food, special pulsating regions, and granules, 

 may generally be observed. They multiply in most cases by dividing 

 into two, but in some cases liberate numerous buds [Arcella), or may 

 rarely form spores {Pelomyxa). They sweat off a protecting cyst in 

 imfavourable conditions. Two individuals may unite in congugation. 

 Most of them occur in fresh water, some in the sea, a few are 

 parasitic. 



Examples. — [a) Naked forms : — Amaba, and the giant amoeba Pelo- 

 myxa; (b) Shelled ioiras,:— Arcella, with a firm (chitinoid) shell; 

 secreting gas bubbles which float it ; and Difflugia, shut in except at one 

 end by a membrane, with foreign bodies such as sand grains glued over it. 

 Magosphcera (Catallacta), a unique form described by Hceckel— (<z) in 

 an encysted phase ; (b) as a free-swimming colony of ciliated cells (like 

 the embryo of some sponges) ; {c) as ciliated units produced from the 

 breaking up of (b) ; (d) as amoeboid forms resulting from modifications 



of the active units. 



4. ZfliJynKMw/jfl'^a, compound forms consisting of a mass of protoplasm 



spreading out into a network, and of numerous spindle-shaped units 

 which travel continually up and down the threads of the living net. 

 Examples.— Labvrinthula (on Algre), Chlamydomyxa (on bog-moss). 



