condition of the changing organic mass. There can be, so far as my
observations go, no certainty as to when, after this, another form of
organism will present itself; nor, when it does, which of a limited
series it will be. But, in a majority of observed cases, a loosening
of the living investment of bacterial forms takes place, and
simultaneously with this, the access of one or two forms of my
putrefactive monads. They were among the first we worked at; and have
been, by means of recent lenses, among the last revised. Mr. S. Kent
named them _Cercomonas typica_ and _Monas dallingeri_ respectively.
They are both simple oval forms, but the former has a flagellum at
both ends of the longer axis of the body, while the latter has a
single flagellum in front.

The principal difference is in their mode of multiplication by
fission. The former is in every way like a bacterium in its mode of
self-division. It divides, acquiring for each half a flagellum in
division, and then, in its highest vigor, in about four minutes, each
half divides again.

The second form does not divide into two, but into many, and thus
although the whole process is slower, develops with greater rapidity.
But both ultimately multiply--that is, commence new generations--by
the equivalent of a sexual process.

These would average about four times the size of _Bacterium termo_;
and when once they gain a place on and about the putrefying tissues,
their relatively powerful and incessant action, their enormous
multitude, and the manner in which they glide over, under, and beside
each other, as they invest the fermenting mass, is worthy of close
study. It has been the life history of these organisms, and not their