GROUP I. THALLOPHYTA : FUNGI. 283 



form of the organism to another, and may modify its physiological 

 activity. 



There is a general resemblance in organisation and reproduction 

 between the Schizomycetes and the Cyanophycese, as well as a 

 remarkable correspondence between individual forms belonging to 

 the two groups. On this ground they are sometimes placed to- 

 gether in a distinct group, the Schizophyta. It is, however, pre- 

 ferable to place them respectively in the classes Fungi and Algae 

 as corresponding sub-cltiesee. 



Sub-Class II. MYXOMYCETES. These organisms are character- 

 istically saprophytic, living on decaying organic substances, such 

 as spent tan, decaying leaves, tree-stumps, etc. 



Their life-history is, in most cases (Endosporese), as follows : 

 On the germination of the spores, the contents of each spore escape 

 as a zoospore, a naked mass of protoplasm, enclosing a nucleus 

 and a contractile vacuole, provided with a single cilium ; this con- 

 stitutes the mastigopod stage, and in this stage the cells multiply 

 by division. After a period of active swimming, the zoospore 

 draws in its cilium, and now creeps about by means of temporary 

 protrusions of its protoplasm termed pseudopodia ; this is the 

 amceboid or myxopod stage, and in this stage also multiplication 

 by division takes place. The amoebae then collect together, cohering 

 into a plasmodium ; the protoplasm of the amoebse in some cases 

 fuses completely so that the plasmodium presents no cellular 

 structure, whereas in others (pscudoplasmodium} the outlines of 

 the coherent amoebse persist ; but, in any case, there is no fusion 

 of the nuclei of the constituent amoebae,, so that the plasmodium is 

 multinucleate and syncytic. 



The plasmodium creeps about, like a gigantic amoeba, by means 

 of pseudopodia, until spore-formation begins. At this time the 

 plasmodium comes to rest ; and it either forms a single sporangium, 

 or divides into several portions each of which forms a sporangium. 

 The mass of protoplasm then assumes the form of the future 

 sporangium ; the external portion of it hardens to form the wall ; 

 while the internal portion, after rapid nuclear division, separates 

 into cells each of which secretes a proper wall and becomes a 

 spore. In most forms a portion of the internal protoplasm goes 

 to form a number of filaments, generally tubular, either free or 

 connected into a net-work, which constitute the capillitium. 

 The wall dries, and eventually ruptures, and' the spores are 

 scattered by the expansion and hygroscopic movements of the 



