CHAPTER X. MORPHOLOGY OF THE BACTERIA. 457 



vinegar, and Scheibler and Durin 1 that those of Leuconostoc mesenterioides, were 

 chiefly composed of the carbohydrate which comes nearest to cellulose ; but it 

 appears probable from the researches of Nencki and Schaffer 2 that in the gelatinous 

 masses (zoogloeae) of purtrefactive Bacteria it consists chiefly of the albuminoid 

 compound which is the principal constituent of the protoplasm of the cell, and to 

 which these writers have given the name of mycoprotein, in combination with 

 infinitesimal quantities of cellulose-like substance. I speak of this as probable only, 

 because it is always a little doubtful how far the substances discovered by 

 macrochemical examination have belonged to the one or the other portion of these 

 minute bodies. 



The membranes are in very many cases colourless ; but in some instances, as 

 has been already said, it is supposed that the intense blue, red, and other hues assumed 

 by some bacteria-masses, and due to colouring-matters resembling anilin dyes, do 

 really belong to the gelatinous membranes, provided they are not excretory products 

 which have found their way into the substratum 3 . The sheaths round the filament of 

 Cladothrix and Crenothrix are often rust-coloured or dark brown from the presence of 

 ferrous hydrate disseminated through their substance. 



Many forms of Bacteria have the free movement of swarm-cells in fluids. 

 Their rapid forward motion is accompanied with rotation round their longitudinal 

 axis, and in many cases with apparent curvature of their bodies. But many observa- 

 tions under the most favourable circumstances have failed to detect in these forms 

 anything like a distinct organ of locomotion. There are however other swarming 

 forms in which extremely delicate filiform processes described as cilia or ' flagella ' 

 have been observed since Cohn's, or even perhaps since Ehrenberg's time; these 

 processes appear at one or both extremities, one usually but sometimes two or even 

 three together, proceeding from the same point. It would appear to be uncertain 

 whether these formations, like the cilia of other vegetable swarm-cells, are parts and 

 processes of the protoplasm and project through the membrane, or whether they 

 belong to, and are appendages of the membrane itself. The grounds which Van 

 Tieghem * alleges for the latter view, namely that no direct connection can be traced 

 between these processes and the protoplasm of the cell, while they behave towards 

 colouring reagents in the same way as the membrane and not as the protoplasm, are 

 against their being true cilia. It is to say the least questionable whether they 

 function as organs of locomotion, considering the irregularity of their occurrence in 

 the forms which are endowed with motion; and it would also be well to enquire 

 whether the so-called flagella or cilia may not vary in character according to the 

 species, and belong in some instances, as for example in Bacillus subtilis, to the 

 membrane, in others, as in the larger arthrosporous species, to the protoplasm. 



According to the shapes in which they appear in the vegetative states a series 

 of principal forms are distinguished : 



1 See Van Tieghem in Ann. d. sc. nat. set. 6, VII, p. 180. 



2 Journ. f. pract. Chemie, neue Folge, 20 (1879), P- 443- 



3 See Schroter, Ueber einige durch Bacterien gebildete Pigmente, and Cohn's Beitrage z. Biol., 

 Heft 2, p. 109 ; also Nageli, Untersuch. ii. niedere Pilze, p. 20. 



* Bull. Soc. Bot. de France, XXVI (1879), P- 37- 



