1914-15.] Fossil Micro-organisms. Ill 
liable to misinterpret the more obvious phenomena that are presented to 
him, any more than he would the similar appearances if investigating the 
putrefactive organisms of a piece of organic tissue that had only recently 
been attacked by micro-organisms. The majority of the rocks submitted 
to examination were both ferruginous and fossiliferous, and consequently 
served very well the purpose I had in view. As will be seen in the context, 
the discovery of iron-bacteria similar to those of the present day was not 
achieved, neither were there evidences of deposits similar to those found in 
the present day in the beds of waters with a high ferruginous content. 
But fossil micro-organisms were found, and one of them evidently had the 
same power of coating itself with a covering of ferric hydroxide, just as the 
present-day iron-bacteria have. 
It was made evident during the course of the investigation that it was 
possible to recognise and obtain details of the life-histories of micro- 
organisms that had been parasitic on the bodies of the organisms that had 
become fossilised. These micro-organisms are here described and their 
existence demonstrated as far as possible at every stage of the investiga- 
tion, with the aid of photomicrographs. This aid is all the more necessary 
in view of the extreme minuteness of the organisms under consideration, 
which would otherwise excuse a certain amount of doubt, as to the possi- 
bility of recognising such small things as bacteria and minute fungi in a 
fossil condition. 
Phycomycites Frodinghamii (Ellis). 
Description of a Ferruginous Fossil Mould from the Jurassic Rocks 
of Great Britain. 
{a) The diagnosis of micro-organisms, even with all the advantages 
which pure cultures afford, is often a matter of some difficulty. The 
diagnosis of fossil micro-organisms must therefore offer considerable 
difficulties, as the investigator is limited almost entirely to morphological 
characteristics. Under the most favourable conditions the following points 
can be elucidated : — 
1. Size, shape, mode of branching, and mode of cell division. 
2. Nature, shape, and size of reproductive organs and of reproductive cells. 
3. Nature of habitat. 
When full information can be obtained with regard to all these points, 
the life-history can be more or less definitely determined, and comparisons 
instituted with modern forms. We may then proceed to assign a generic 
and a specific name to the organism in question. 
