Slime Moulds, Bacteria, and Yeasts. 253 



about in moist and dark places, avoiding the light and being 

 attracted by moisture ; but when it is ready to form its 

 spores, it creeps away from its former habitat and seeks the 

 light at the surface of the log or of whatever substratum it 

 is inhabiting. While in the plasmodium stage, it sends out 

 arms here and there that may surround and engulf bits of 

 organic matter, which it digests and employs as food. It 

 does not possess chlorophyll, and is not, like green plants, 

 able to manufacture its own food ; for this reason it is 

 restricted in its habitat to the remains of higher plants 

 which yield the organized materials necessary to it. 



151. Formation of Spores. When ready to produce 

 spores, the plasmodium puts forth outgrowths which be- 

 come sporangia, the forms of which vary with the species 

 (see Fig. 132, 8 and 9). At the surface of the sporangia a 

 crust, and sometimes a variously reticulated framework, is 

 formed, while the interior protoplasm breaks up into 

 numerous spores. Sometimes, among the spores, threads 

 are formed which twist and untwist with the changing 

 humidities of the atmosphere, and thus aid in loosening the 

 spores preparatory to their dissemination by the wind. 



When a spore falls into a wet place, its protoplast, which 

 is the essential part of it, creeps out from its wall, and 

 (Fig. 132, 7) being provided with a cilium, swims about 

 in the water. After a time the cilium becomes absorbed, 

 and the protoplast creeps about and obtains particles of 

 food by surrounding them bodily (6). While in this con- 

 dition it may multiply by repeated division. Finally, many 

 protoplasts may fuse together and form a larger multinucle- 

 ated body similar to the slimy plasmodium with which this 

 description began (see Fig. 132). 



It often happens that when the substratum is drying up 

 the plasmodium changes into dry masses of various shapes, 



