CHAPTER X.—-MORPHOLOGY OF THE BACTERIA. 455 
Little is known of the more intimate construction of the cells of the Bacteria, 
owing to their minute size. All that can with any confidence be affirmed of the 
greater part of them is founded less on direct observation than on the analogy of the 
larger cells of other organisms, with which they agree in their chief characteristics so 
far as these can be recognised, and with which they are also connected by inter- 
mediate forms. 
The protoplasm of the cell in most forms and even in the larger ones appears, 
when in a state of active vegetation, to be a homogeneous and faintly refringent 
mass filling the cell-cavity. Distinct little granules (microsomata), the constitution 
of which is still undetermined, may be distinguished occasionally in the larger 
forms in this condition. They appear in greater abundance as the vegetative 
activity diminishes, and the protoplasm may then be still more frequently seen to form 
a parietal layer inclosing a pellucid central cavity. Highly refringent (crystalline) 
granules of sulphur, which owe their origin to the decomposition of the sulphates by the 
plant, are often imbedded in considerable quantity in the protoplasm of the species of 
Beggiatoa which grow in springs containing sulphur, as was first pointed out by 
Cramer and Lothar Meyer. 
The protoplasm of some species which appear to belong to this group forms: 
chlorophyll, and seems to be coloured green throughout by this substance. Van 
Tieghem found two forms of this kind living in water, which he distinguishes as 
Bacterium (Arthrobacterium) viride and Bacillus virens!; W. Engelmann a third 
marked by the very pale tint of its chlorophyll, which he names Bacterium 
(Arthrobacterium) chlorinum ?. 
Most species are distinguished by the absence of chlorophyli and analogous 
colouring-matters. In this respect they agree with the Fungi, and it is owing to this fact 
and its physiological consequences that they have received the name of Fungi. In’ 
some species, Zopf’s Beggiatoa roseo-persicina for example and its subordinate forms, 
the protoplasm is uniformly tinged with a red colouring-matter, which Lankester has 
carefully examined and named bacteriopurpurin*. It is not yet certainly ascertained 
whether the colouring matters, which often give an intensely red, blue, yellow, or 
other tint to the gelatinous accumulations of some small forms, such as Micrococcus 
prodigiosus, are contained in the membranes only or are attached also to the 
protoplasm, 
Some species which contain no chlorophyll form a substance in their protoplasm, 
which from its behaviour with reagents and the physiological relationships observed in 
certain cases, must be considered to be more or less like starch, or more correctly 
granulose. The cells of Prazmowski’s Bacillus (Clostridium) butyricus (Amylobacter 
Clostridium, Trécul) and Spirillum amyliferum, van Tieghem‘, become more highly 
refringent in the stages which precede the formation of spores (section CXXX), and their 
protoplasm then assumes a blue or violet colour with solution of iodine, either 

1 Bull. Soc. bot. de France, 27 (1880), p. 174. The figure there given by Van Tieghem from - 
Perty is interesting, but it must remain a question whether it belongs to this group. 
2 Bot. Ztg. 1882, p. 323. 
® Quart. Journ. of Micr. Sc., New Series, XIII (1873), p. 408. 
* See Prazmowski, Unters. ii. d, Entwickgsg. u. Fermentwirk. einiger Bacterienarten, Leipzig, 
1880, and Van Tieghem in Bull. Soc. Bot, de France, XXVI (1879), p. 65. 
