172 ] The Classification of Lower Organisms 



Predatory Mycetozoa producing macroscopic fruits, these producing internal uni- 

 nucleate spores. The type is Lycogala, the sole genus of the order as originally 

 published. 



The fruits of many examples are of the appearance of minute puffballs, and Per- 

 soon and Fries classified them as puffballs; Fries took note that they are primitus 

 mucilaginosi and made them a suborder distinct from the proper pufTballs. De Bary 

 studied the non-reproductive stages; concluded "dass die Myxomyceten nicht dem 

 Pflanzenreiche angehoren, sondern dass sie Thiere, und zwar der Abtheilung der 

 Rhizopoden angehorig, sind"; and renamed the group Mycetozoen. This name was 

 apparently first published in Latin form, in the category of classes, by de Bary's stu- 

 dent Rostafinski. Conventional botany continues to list Myxomycetes as a class of 

 Fungi; conventional zoology makes the group an order of Rhizopoda or Sarcodina. 



The spores germinate readily in water or appropriate solutions (Jahn, 1905; Gil- 

 bert, 1929; Smith, 1929). Their nuclei usually divide once or twice, during or just 

 after germination; thus each spore produces from one to four naked cells. 



It is in germinating spores that mitosis is most easily observed. Mitosis takes place 

 in a clear area, about which some observers have found a persistent nuclear membrane. 

 The spindle is sharp-pointed. Only a few observers (as Skupienski, 1927) have dis- 

 cerned definite centrosomes. When the one or two divisions associated with germina- 

 tion are complete, the flagella grow forth from the areas of the poles of the mitotic 

 spindle. All earlier observers described the spores as uniflagellate, but Ellison (1945) 

 and Elliott (1949) found them biflagellate. The flagella may be apparently equal or 

 moderately unequal; or one of them may be very brief. Each nucleus remains con- 

 nected to the base of the flagella by a conical body of clear protoplasm, the Geissel- 

 glocke of Jahn (Jahn, 1904; Howard, 1931). 



The flagellate cells are not spores, but gametes; they fuse with each other. Skupien- 

 ski (1917) affirms that they are of two mating types. Fusion is at first by pairs, and 

 Howard (1931) found that each zygote develops into a plasmodium by itself. All 

 other observers (de Bary, 1858, 1859; Cienkowski, 1863; Skupienski, 1917, 1927; 

 Schiinemann, 1930) have found the zygotes to fuse with each other and with further 

 gametes. The flagella are lost. The nuclei fuse in pairs; those which fail to find 

 partners are digested. 



The cell formed by the fusion of zygotes and gametes is a young plasmodium. The 

 term was coined by Cienkowski ( 1863, p. 326) : "Das Protoplasmanetz der Myxomy- 

 ceten werde ich mit den Namen Plasmodium bezeichnen." The plasmodium nour- 

 ishes itself in predatory fashion, on fungus spores, bacteria, and other digestible ob- 

 jects, and grows accordingly. Mitosis occurs simultaneously in all nuclei of the plas- 

 modium, and takes 20 to 40 minutes; it has accordingly only rarely been observed 

 (Lister, 1893; Howard, 1932). Plasmodia do not ordinarily divide, but grow to great 

 sizes. They are not very familiar objects because during most of their life they keep to 

 dark and moist places, chiefly among vegetable remains. Drouth does not kill them; 

 they can become dry and hard while retaining the capacity to resume activity upon 

 the return of moisture. When an active plasmodium reaches a certain stage, its re- 

 actions change; it moves out into the light and to dry places. A plasmodium in this 

 stage is conspicuous, being of the form of a network which may be many centimeters 

 in diameter, in some species brilliantly colored. The whole is a single naked protoplast. 



Each Plasmodium proceeds to produce a fruit or fruits. The entire mass may heap 

 itself up, or it may break up into portions, large or minute. In species whose plas- 

 modia break up into small fragments, each of these may secrete a column of lifeless 



