CHAPTER I* 



ELEMENTS OF MICROBIAL CYTOLOGY 

 CELLS AND ENERGIDS 



The microorganisms are confined to cells, such as algae, molds, 

 bacteria, yeasts, and protozoa, or cytoplasmic masses with a nucleus 

 associated with each (Fig. 3). Some are, however, made up of rows 

 of cells, such as threads of Cladothrix, occasionally capable of branching 

 out, like the mycelium of a mold (Fig. 4, A). There are also some cells 

 which have a special structure. In each cell are enclosed several 

 nuclei. If certain amoabee are examined, for example, Pelomyxa pa- 

 lustris (Fig. 4, B), inside of what appears to be a cell there are found 

 many nuclei. Such cells have not the anatomical value of true cells, 

 but seem to represent as many cells as there are nuclei. Each of 

 these nuclei with the cytoplasm which surrounds it, equivalent to a 

 cell, may be called specifically an energid. Some algae and fungi are 

 made up of threads of cells enclosing several nuclei; each cell in- 

 cluded in a thread consequently represents a group of organized ele- 

 ments, the union of several energids in the same anatomical unit (Fig. 

 4, A). 



STRUCTURE OF THE CELL 



A typical cell is constituted of three essential elements : the nucleus ; 

 the cytoplasm; and the cell-membrane. 



The general characteristics of these three elements, and, follow- 

 ing this, the study of cell reproduction, may now be systematically 

 presented. 



THE NUCLEAR STRUCTURE. General Structure of the Nucleus. The 

 nucleus frequently takes in microorganisms the typical form which it 

 assumes in the higher organisms, namely, that of a spherical vesicle 

 limited by a membrane, enclosing a hyaline substance called the 

 nuclear-fluid, or nucleoplasm (Fig. 22, A, a, B, a). In this nuclear 



*By A. Guilliermond. 



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