126 Proceedings of the Koyal Society of Edinburgh. [Sess. 
spiral forms, probably because these organisms did not flourish in sur- 
roundings which lent themselves to fossilisation. It is possible, of course, 
that by this time spiral bacteria had not yet been evolved. The facts at 
our disposal throw no light on this point. There is one point, however, 
which cannot be too strongly emphasised, viz. the futility of any attempt 
to identify fossil bacteria with those in existence at the present day. If 
the difficulties of identification of modern bacteria are so great when 
we can command the aid of cultural experiments, what must be thought 
of the difficulties which attend the identification of fossil bacteria ? Even 
when all the data which it is possible to obtain with regard to any 
particular fossil species have been gathered, the information might still 
apply to a hundred or more species if they were in any way similar to 
modern bacteria, and there is no reason to suppose that they were in any 
way different. It seems to me that the utmost that can be achieved is to 
allocate the fossil forms that are discovered to their proper genera, and 
then note the size and the habitat. An accumulation of facts of this kind 
should ffive us in time a mass of interesting information from which a few 
general laws with regard to the past of fossil bacteria may be gleaned, but 
we must not expect too much from such scanty data. In Renault’s work 
an attempt is made to identify some of his fossil species with well-known 
species that cause putrefaction at the present day. Further, some of his 
conclusions with regard to such organisms as Bacillus Tieghemii — bacillus 
discovered after maceration of fossil plants — cannot be maintained. For 
instance, he refers to the germination of a spore in situ, before its liberation 
from the bacillus which produced it. He writes : Au milieu des bacilles 
on trouve de nombreuses spores, qui sont a divers etats de germination.’ 
Even in the case of modern bacteria this illusion often results when one 
bacillus is superimposed on another in such a way that the end of one lies 
on top of or underneath another, and gives the impression of having 
germinated directly out of the other. Such being the case, how much more 
probable that this illusion would be presented by bacteria in the fossil 
condition ! His figures bear out this interpretation. He also refers to the 
discovery of free spores, but it is doubtful whether the specks referred to 
by him can be referred to these structures. Apart from these points, 
Renault’s contribution must rank as epoch-making in this branch of 
bacteriology. 
(b) Bacteria from the Gault, Folkestone. 
The rock containing these bacteria was a nodule from the base of the 
Gault, Folkestone. Under the microscope, a slide cut from the nodule pre- 
