brane could be resolved by mechanical means into rods that 
I understood the real nature of the membrane. As the struc- 
ture (if one may call it so) becomes thick enough to form a 
visible scum, the arrangement of the particles can no longer 
be made out, for it is not possible to subject it to examination 
without dislocating it to such a degree as to render their 
relative positions indistinguishable. 
When common microzymes grow on moist surfaces, they 
with their intervening jelly sometimes form viscous masses of 
sufficient size to be cognoscible by the unaided senses, these 
consisting of a material similar to that of the “‘ scum” which 
forms on the surface of liquids in which microzymes are 
growing. ‘This fact is expressed by the term Zooglea applied 
to such masses or colonies of microzymes by Cohn. 
It is on observations made as to the growth of microzymes 
in colonies that the little which can be stated as to the form 
in which they originate is based. In the spheroidal masses 
above referred to, and indeed whenever microzymes occur in 
a gelatinous matrix which can be distinguished, we observe 
foci of growth at which the particles are indefinitely minute 
and spheroidal; around these foci there are zones of matrix, 
already obsolete and disintegrating, which are inhabited by 
staff-shaped microzymes of larger size, which eventually 
become free and display their proper movements. Here 
therefore it seems probable that bacteria come into dis- 
tmguishable existence not as rods but as spheroids. Sub- 
sequently they multiply, as is well known, by division. 
As to the conditions of their origin there is even less 
knowledge and more difference of opinion. There being an 
immense preponderance of evidence that they do not spring 
into existence of themselves in the media in which they grow, 
most observers have looked for germs in the atmosphere, but 
with no success. Nor has anyone excepting Professor Hallier 
even suggested a plausible theory on the subject. Liquids 
which contain no particle distinguishable under the highest 
powers of the microscope can often (as will be hereafter 
shown) be proved to possess the property of evolving 
microzymes without contact with external media, and must 
therefore contain the germinal substance from which these 
organisms spring. In interpreting this fact it may be sup- 
posed either that the germinal substance is universally and 
equally distributed, 2. e. dissolved in such liquids, or that it 
_ is unequally distributed or particulate. That any living sub- 
stance is soluble in water is not at present admissible; we 
must therefore accept the other alternative, and believe that 
we have to do with particles so minute that they do not 
