SYSTEMATIC SURVEY. 99 



little capsules which arise from the surface of the plasmodium, and are 

 often elaborate in structure. The spores may have a brief flagellate 

 activity, and then sink down into amoeboid forms, or may be at once 

 little amoebae ; the amoebae grow and consequently multiply and, after a 

 while, collect into the characteristic fused masses or plasmodia, which 

 sometimes spread over several square inches. 



FIG. 25. Diagram of Protoniyxa atirantiaca. (After H^CKEL.) 



i. Encysted ; 2. Dividing into spores ; 3. Escape of spores, at 

 first flagellate, then amoeboid ; 4. Plasmodium, formed from fusion 

 of small amoebae. 



Example. Fuligo or ^Ethalium septicum, " 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 allied to Fungi, 

 and it is natural that some of these primitive forms should appear to 

 hesitate between the two paths, f Krukenberg's discovery of a peptic 

 ferment and an acid in these forms is an interesting illustration of the 

 general similarity of digestive processes in all organisms.') 



B. Predominantly Amoeboid 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 en- 

 gulfed along with the food, special contractile vacuoles, and granules, 

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

 into two, but in some cases liberate numerous buds (Arcelld], or may 

 rarely form spores (Pefatuyxa). They sweat off a protecting cyst in 

 unfavourable conditions. Two individuals may unite in conjugation. 

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

 parasitic. 



Examples. (a) Naked forms: Amceba, and the giant amoeba Pelo- 

 myxa ; (b) Shelled forms : 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 Heeckel (a) 

 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 modifica- 

 tions of the active units. 



4. LABYRINTHULIDEA, compound forms consisting of a mass of proto- 

 plasm spreading out into a network, and of numerous spindle shaped 

 units which travel continually up and down the threads of the living 

 net. 



