6 THE MYXOMYCETES 



distilled water, but their behavior is often highly erratic, so that the 

 accounts of different students are not in complete accord either as to 

 the fact of germination in a given species or as to the time and manner. 

 Nearly all agree that the spores of Reticularia lycoperdon and Fuligo 

 septica germinate quickly and easily, as do those of many species of 

 Physarum. Other forms germinate slowly and with difficulty. Among 

 the factors which seem to influence germination are the age of the 

 spores, the circumstances under which they were formed and the 

 H-ion concentration of the medium. Doubtless others will be added. 

 At germination the spore wall breaks and from one to four swarm- 

 cells emerge. Sometimes the protoplasmic contents pass out as a 

 vesicular mass and then become differentiated into one or more swarm- 

 cells. The swarm-cell is comma-shaped, with an anterior flagellum 

 attached by its base to a bell-shaped body adjoining the anterior 

 nucleus. The posterior end is more or less amoeboid and contains a 

 large vacuole. The swarm-cell moves in a jerky fashion in a more or 

 less spiral path, feeding on bacteria and fungus spores, and probably 

 taking in nutrient materials in solution when such are present. Even- 

 tually it settles down, loses its flagellum and divides into two similar 

 cells which develop flagella. This process may continue for some time 

 but eventually the swarm-cells function as gametes, fusing in pairs. 

 The zygote thus produced is the first stage of the young plasmodium. 

 It feeds and grows and the nuclei divide. It may also fuse with other 

 Plasmodia. Cienkowski (1863), who gave the plasmodium its name, 

 believed it always arose from the fusion of numerous swarm-cells, but 

 recent studies throw doubt upon this. Wilson and Cadman (1928) 

 show that in Reticularia lycoperdon swarm-cells which have failed to 

 fuse may be incorporated into the zygote, but they serve as food-mate- 

 rials, the nuclei being destroyed and absorbed with the protoplasm. 

 This, of course, alters the conception of a plasmodium as Cienkowski 

 interpreted it and as it has been incorporated in the literature; but the 

 term is so useful as a designation for the naked, multinucleate, assim- 

 ilative phase of the slime molds that it seems well to retain it in its 

 altered sense. There can be no question that large plasmodia fuse. 

 When grown in culture, a single plasmodium in its progress across the 

 substratum may break up into two or more separate plasmodia. These 

 usually meet sooner or later and become completely incorporated 

 without the least difficulty. It cannot be regarded as proved, however, 

 that the origin of the plasmodium is always from the fusion of two 

 gametes. Schiinemann (1930), working with Didymium nigripes and 

 other species, showed that several swarm-cells may unite to form a 

 Plasmodium with haploid nuclei and that nuclear fusion occurred in 



