136 THALLOPHYTA. [CH. 



of bones which were attacked by Bacteria. I am indebted to 

 Prof. Renault for an opportunity of examining specimens of 

 this and other fossil Bacteria, and in this particular case there 

 is undoubtedly strong evidence in favour of the author's deter- 

 mination. 



Bacillus Tieghemi Ren.^ and Micrococcus Guignardi Ren.^ 

 (Fig. 28 A.) 



Renault has given the name Bacillus Tieghemi to certain 

 minute rods 6 — 10/tt in length, and 2"2 — 3'8/a broad, often 

 containing a dark coloured spherical spore-like body 2/x. in 

 diameter, which have been found in the tissues of a Coal- 

 Measure plant. 



The name Micrococcus Guignardi has been applied to more 

 or less spherical bodies 2"2/a in diameter, also met with in 

 silicified plants. 



A portion of one of Renault's figures is reproduced in 

 Fig. 28 A. The faint and broken lines mark the position of the 

 middle lamellae of parenchymatous cells from the pith of a 

 Calamite. The tissue has been almost completely destroyed, 

 but the more resistant middle lamellae have been partially 

 preserved. The short and broad rods represent what Renault 

 terms Bacillus Tieghemi ; the small circle in the middle of some 

 of these being referred to as a spore, and in oije specimen 

 shown in the figure, the second rod at right angles to the 

 first is described as a small daughter-Bacillus formed by the 

 germination of the central spore. 



The isolated circles in the figure are referred to Micrococcus. 



It is unnecessary to give an account of the numerous 

 examples of Micrococci and Bacilli described by Renault from 

 Devonian, Carboniferous, Permian and Jurassic rocks. We may, 

 however, in a few words consider the general question of the 

 existence and possible determination of fossil' Bacteria. 



In 1877 Prof. Van Tieghem' of Paris drew attention to the 

 method of operation and plan of attack of Bacillus amylobacter 



' Eenault (95^) p. 17, fig. 9, (96i) p. 460, fig. 102, and (963) p. 292, fig. 10. 

 ^ Benault (96S) p. 297, fig. 14. a Van Tieghem (77). 



