THALLOPHYTA— FUNGI 



75 



spherical (Microco(3Cus), some more elongated or rod-shaped 

 (Bacterium), some forming a spiral (Spirillum). The multi- 

 cellular forms are filaments, branched or mibranched, or small 

 masses of cells. Thej^ are extremely polymorphic, one organism 

 passing through several forms in its life history. Some are 

 furnished with cilia, b^^ which they move rapidl}^ in the medium 

 in which they live {fig. 828). 



The cells are of a very simple structure, consisting of a cell- 

 wall enveloping a mass of protoplasm. In this is fomid a body 

 capable of staining more deeply than the rest of the cell- 

 contents, and hence thought to be a nucleus. The protoplasm 

 often contains deeplj^ staining granules, sometimes regularly 

 disposed round the cell. The true nature of the staining 



Fig. 828. 





Fig. 828. 



1. Sarcinfe. 



2. Bacteria. 



3. Spirilla, 



4. Spirillum, show- 



ing flagellEe. 

 I Micrococci in 

 strings, singly 

 and in groups. 

 After • Cohn 

 and Sachs. 

 (Very highly 

 magnified.) 



material is, however, not j^et accurately ascertained. Man}' of 

 these cells contain various pigments. 



In the course of their life history-, most of the Schizomycetes 

 become embedded in a jellj^-like substance which holds great 

 numbers of them together. This is known as the zoogloea stage. 

 The zoogloea may form a membrane or scum on the surface of 

 the liquid in which the organism is living, or may occur in the 

 shape of masses of various forms. 



The reproductive processes are either vegetative or asexual. 

 In the former case the multiplication takes place with enormous 

 rapidity bj^ ordinary cell-division. In the second case spores 

 are formed, one in a cell, by a process of rejuvenescence. A 

 filament may thus give rise to a chain of spores, which ulti- 

 mately become separate by the degeneration of the original cell- 



