Scientific Memoirs by
them. This, however, is no sufficient ground for omitting to notice the results
which a series of careful observations have appeared to lead to.
Attention was primarily directed to this subject first by the observation
that certain modifications in form appeared to characterise many of the
commas which had been developed in substrata which had not been fully neu
-tralised, and which therefore retained a slightly acid reaction, and secondly by
the occurrence in a series of alkaline tube cultivations of a gradual development
of a series of forms similar to those described and figured by Dr. Klein as charac
-teristic of agar-agar cultivations conducted at the ordinary room-temperature in
winter in London.
In the case of several plate cultivations on faintly acid agar-agar jelly it
was noticed that, whilst commas were abundantly developed, many of them when
compared with the typical slender commas of neutral or alkaline cultivations
were characterised by their relative thickness and shortness. On examining
them more closely, too, such commas were in many instances observed to pre
-sent appearances which were for some time regarded as indicative of the incipient
stages of spore formation. These consisted in the presence of colorless areas in
the substance of the stained protoplasm (Plate III, Fig. 1A). The number of such
spaces varied in individual instances, being in great part apparently related to the
size of the commas in which they originated, short specimens containing only one
colorless area whilst longer ones contained two or even three. In general appear
-ance they very closely resembled spores in an early stage of development, but, in
spite of the most careful observation, no further evidences of spore-formation
ever occurred, and it ultimately became evident that they were not due to any
process of that nature but to one of mere vacuolation of the protoplasm.
Numerous observations were now undertaken with a view to determine more
accurately how far variations in the character of the substrata appeared to be
capable of influencing the form of commas developed in them. In the course of
these observations two distinct series of experiments were tried. In the first of
these, cultivations—both on plates and in tubes—were simultaneously started
from a common source, consisting of a pure tube cultivation of commas, in me
-dia of various reactions and the characters of the resulting growths carefully
compared with one another. In the second series the effect of repeated altera
-tions of various reactions was studied, materials derived from alkaline or neutral
substrata being cultivated in acid ones, and the resultant crops being used as a
source of materials for fresh alkaline cultivations.
The result of the first series of experiments was to show that while in neu
-tral or feebly alkaline media crops of typical slender commas were developed,
in the case of acid cultivations these were more or less replaced by shorter and
relatively thicker forms, which in many instances ceased to shew any morpho
-logical evidence of their commatous origin. On comparing the results of parallel
cultivations in feebly and strongly acid media corresponding differences in degree
of deviation from the standard alkaline type regularly manifested themselves.
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