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Scientific Memoirs by
which they subsequently produce is no evidence of their specific identity. The
abortiveness of the growths is evidence of the common action of previous
exposure to a special environment, but the resemblance between the resultant
abortive growths is of no value as evidence, one way or other, in regard to the
question of specific identity. No one would propose to determine the species
included in any genus of the higher plants by comparing the characters of
abortive seedlings which had been developed under highly unfavourable cir-
cumstances, and had therefore failed to show characteristic differences, and
where dealing with organisms, such as schizomycetes, which are so conspicuously
modified by the nature of their environment, it is even less rational to adopt any
such procedure.
Prolonged cultivation in neutralised agar-agar media certainly tends to
produce general assimilation in most forms of choleraic comma-bacilli in one
respect, namely, in their capacity for giving rise to those changes in bouillon
which lead to the appearance of the so-called cholera-purple on the addition
of acids. Some forms from the very outset possessed this property in high
degree, whilst others when first obtained were almost entirely wanting in it,
but at present, after months or years of continued cultivation under like con-
ditions all, save one or two exceptional forms, alike possess it in high degree.
For example, forms η and ς, which originally hardly showed any capacity,
are now as highly endowed with it as any of those which from the first pos-
sessed it in high degree. The phenomena are just what might have been ex-
pected from the evidence, which has been already alluded to in connection with
potato-cultures of certain forms, and which shows that the property is one which
is specially liable to undergo modification under the influence of alteration in
the nature of the environment. The initial differences are no doubt due to minor
variations in the exact constitution of the original source from which the forms are
primarily obtained, and they naturally tend to disappear under the influence of
continued exposure to like conditions favouring the acquisition of the property.
Even here, however, assimilation is not universal, for the form which was described
as δ in my previous paper has never acquired the property in the slightest degree,
and form λ, which originally possessed it in slight degree, now, after continued
cultivation for more than a year-and-a half, shows no perceptible increase in it.
In the case of most of the forms cultivations in bouillon, in other respects,
exhibit no phenomena of truly diagnostic value, but in one or two instances
very conspicuous peculiarities are present. Forms ι a n d
λ r e s e m b l e o n e
another in this respect, although the former is highly endowed with the capacity
for giving rise to cholera-purple, whilst the latter is only feebly endowed
with it.
Cultivations of ι a r e i n v a r i a b l y d i s t i n g u i s h e d f r o m t h o s e o f a l l t h e o t h e r
forms capable of determining the presence of cholera-purple by the extreme
slowness and feebleness with which clouding of the fluid takes place, and