186 HANDBOOK OF PROTOZOOLOGY 



engulfs bacteria by means of its pseudopodia and grows in size. 

 It multiplies by binary fission. In this process, the flagellum is 

 withdrawn and the body becomes rounded. The nucleus under- 

 goes a mitotic division, followed by a cytoplasmic constriction 

 to form two daughter individuals {o-q). The multiplication 

 seems to be repeated. The myxoflagellate may often become 

 rounded and secrete a hyaline cyst-wall, thus forming the 

 microcyst (r), which loses its flagellum permanently and trans- 

 forms itself into a myxamoeba(5). The latter, through fusionwith 

 many others, produces the Plasmodium described above. This 

 is the general life-cycle of a typical endosporous mycetozoan. 



In the genus Ceratiomyxa, the only genus of the exosporous 

 form, in which spores are produced on the surface of sporo- 

 phores, the development is briefly as follows: The Plasmodium 

 lives on or in decayed wood and presents a horn-like appearance 

 (sporophore). The body is covered by a gelatinous hyaline 

 substance, within which the protoplasmic movements may be 

 noted. The protoplasm soon leaves the interior and accumu- 

 lates at the surface of the mass; at first as a close-set reticulum, 

 and then it becomes differentiated into a mosaic of polygonal 

 cells, each containing a single nucleus. Each of these cells 

 moves outward at right angles to the surface, still enveloped 

 by the thin hyaline layer, which forms a stalk below it. These 

 cells are the spores, which become ellipsoidal and are covered 

 by a resistant membrane when mature. The spore is uninucle- 

 ate at first, but soon becomes tetranucleate. When a spore 

 reaches the water, the contents emerge as an amoebula which 

 then divides three times, forming eight small bodies, each of 

 which develops a flagellum and becomes a myxoflagellate. 

 The remaining part of the development is presumably similar 

 to that of the endosporous mycetozoan. 



An enormous number of mycetozoan genera are known. 

 The order is here divided into two suborders according to Lister. 

 Further division into tribes, legions, sublegions, and families 

 is given below, together with one or two genera for each family. 



Spore develops into myxoflagellate; myxamoebae fuse completely and 



form the Plasmodium Suborder 1 Euplasmodia 



No flagellate stage; myxamoebae grouped prior to spore-formation, but 



do not fuse to form a true Plasmodium Suborder 2 Sorophora 



