1914-15.] Fossil Micro-organisms. 125 
factive micro-organisms. So that, in a large number of these organic 
fragments which make up the greater part of fossiliferous stones, the 
effects of the ravages of micro-organisms must be there. The question 
therefore arises as to whether these effects can be identified with any 
degree of certainty. We can thank the improvements in modern technique 
for the fact that it is possible to speak with certainty. It is possible to 
make slides so extremely thin that they can be brought into focus when 
examined microscopically even when a immersion lens is employed. 
There is nothing that I know of which resembles the appearance presented 
under the microscope by a mass of bacteria feeding on its host, and retains 
this resemblance when observed under the highest powers of the micro- 
scope. Under a low magnification certain minute dots on the slide might 
give the impression that remains of bacteria were being observed, but 
this impression could not be kept up if the same dots be examined at a 
magnification of 1500 to 2000. For the individuals in a bacterial mass are 
usually short rods, rounded at the ends, uniform in thickness, and all 
conforming to one or two sizes. When these conditions are found inside 
a fragment known to be of organic origin, it is reasonable to make the 
same deductions as would be made in an examination of organic matter 
that had only recently undergone putrefaction. There is nothing in 
nature that can imitate this appearance at a magnification when even 
bacteria become comparatively large objects. A glance at Plate II, fig. 8, 
photographed at a magnification of 400, will make this point clear. When, 
further, a closer examination of the same reveals figures similar to those 
shown in fig. 21, which in size and shape and in every other respect 
resemble modern micrococci, the case for the presence of bacterial forms 
in these fossil organic fragments becomes complete. We see in these fossil 
organic fragments the same combination of bacterial forms that we see 
in any piece of putrefying flesh that we examine under the microscope, 
viz. a mixed bacterial life in which members of the rod-shaped bacteria 
play the more prominent part, and members of the round or coccus bacteria 
the less prominent role. 
The only notable work that has previously appeared on this subject 
is that of Renault (6), who in 1896 found bacteria in the vessels of fossil 
trunks of Cycas and other plants, in the interior of coprolites, in the 
interior of sporangia, etc. There can be little doubt that Renault actually 
observed either the bacteria themselves or spaces that had originally been 
filled with bacteria. The rod forms — Bacillus or Pseudomonas — easily 
predominated ; and amongst them, playing a less prominent part, were 
members of the round forms — coccus group. No traces were found of the 
