188 THE MICROSCOPICAL NEWS, 
to which I now allude. That they are not merely the concomitants 
of putrefaction and disease, I think there is abundant evidence to 
show, but to what extent they are the producing causes of many of 
the phenomena which have been ascribed to their agency, it would 
appear that further investigation is necessary to decide ; especially 
when we consider the enormous multitudes in which the harmless 
bacteria are produced, the little that is known of their life-histories, 
the difficulty which the best observers have found in differentiating 
the minute and homogeneous forms, and the frequency with which 
other minute particles, organic granules, and even fat globules, 
have been taken for such minute globular organisms as A@zcrococcus, 
or the spores of the larger bacteria. It is even possible, as some 
writers suppose, that the smallest globular forms are merely the 
spores of the rod-like and filamentous ones; and that the latter 
are only different phases in the development of higher vegetable 
organisms, the life-cycles of which are yet incompletely known. 
Some observers even profess to have traced the transformation of 
a Micrococcus into a Mucor or an Ustilago, amongst the true fungi ; 
others claim to have witnessed the development of bacteria into 
yeast fungi, and these again into the form of Penicillium. ‘This 
polymorphism has not yet been demonstrated; and all that is 
really known as to the transformations of the Bacteriacez relates 
to spore formation and development, and the different modes in 
which the cells colonise or group themselves. It is generally 
believed that true sporangia have been really seen in some species 
of Bacillus. 
The Bacteriaceze are found either as single independent cells, or 
united together in the form of chains or filaments, or imbedded in 
a gelatinous matrix, which serves to mass them together in a some- 
what globular form. There are five forms in which these organisms 
are found attached to each other, or growing in masses. 
1. The Zorula form ; caused by spherical, oval or oblong cells, 
after undergoing multiplication by transverse division, remaining 
attached to each other in a single constricted chain, like the cells 
of yeast. 
2. The Leptothrix form ; when a number of cells are united in 
a filament, not separated by constrictions. 
3. The Zooglwa form ; when spherical or oval cells, during rapid 
growth, are massed together in a homogeneous, colourless mucilage, 
secreted by themselves, forming a globular or irregular mass, some- 
times several centimetres in diameter. 
4. The AZ; coderma form; when the cells unite to form a thick 
layer on the surface of the fluid, without an intervening mucila- 
ginous substance ; probably caused by a demand for oxygen. 
5. Swarms. ‘The spiral and filamentous species, when actively 
multiplying, appear in swarms; and as their motions are not im- 
