5. Those who say that the bacterial cell contains a distinct nucleus, at least in most instances. These authors base their claims on staining with a Giemsa stain. (Feinberg, Ziemann, Neuvel, Dobell, Douglass and Distaso). That nucleoproteins are present in the bacterial cell in relatively large amounts is well established. Also that there are other proteins and that the protoplasm is not all nuclein. Some workers as noted above have been able to demonstrate collections of nuclein by staining, especially in very young cells. In older cells this material is in most instances diffused throughout the protoplasm and can not be so differentiated. The following statement probably represents the generally accepted view at the present time: A nucleus _as such_ is not present in bacterial cells, except in a few large rare forms and in very young cells. _Nuclein_, the characteristic chemical substance in nuclei, which when aggregated forms the nucleus, is scattered throughout the cell contents and thus intimately mingled with the protoplasm, and cannot be differentiated by staining as in most cells. The close association of nuclein and protoplasm may explain the rapid rate of division of bacteria (Chapter VIII, p. 91). The chemical composition of the bacterial cell is discussed in Chapter VII. In addition to the _essential_ parts just described the bacterial cell may show some of the following _accidental_ structures: _vacuoles_, _capsules_, _metachromatic granules_, _flagella_, _spores_. =Vacuoles.=--_Vacuoles_ appear as clear spaces in the protoplasm when the organism is examined in the living condition or when stained very slightly (Fig. 18). During life these are filled with liquid or gaseous material which is sometimes waste, sometimes reserve food, sometimes digestive fluids. Students are apt to confuse vacuoles with spores (p. 47). Staining is the surest way to differentiate (Chapter XIX, p. 209). If vacuoles have any special function, it is an unimportant one. [Illustration: FIG. 19.--Bacteria seen within capsules.] [Illustration: FIG. 20.--Metachromatic granules in bacteria. The dark round spots are the granules. The cells of the bacteria are scarcely visible.]