THE BIOLOGY OF MICROBES, ETC. 167 



generally arranged in bundles (Fig. 38), which may 

 be interwoven with one another. Each thread is 

 divided into short rods, from 1 to 1'2 //, broad, and 

 from 2 to 10 //, long. This microbe is believed to 

 be connected with dental caries. 



Leptothrix innominata. This microbe is usually 

 found on the soft white matter which is deposited 

 on the teeth. The threads are from 0'5 to 0*8 p in 

 breadth. 



Leptothrix parasitica. The threads are slender, 

 not articulated, loosely felted, and for the most part 

 curled. They measure 

 from 100 to HO /* in 

 length, and about 1 ^ in 

 breadth, and occur both 

 in still and running water. 

 This bacillus (Fig. 33, 22) 

 is best cultivated on in- 

 fusions of rotting algae and 

 animal substances. This 

 microbe is believed by Plo . 38 . LEPTOTHBIX BucCAUS . 

 Zopf and others to give 



rise to micrococci, bacteria, etc. ; in other words, 

 it is a pleornorphic form, but Zopf s observations 

 were not made after exact methods. 



Beggiatoa roseo-persicina. This is the ' peach- 

 coloured bacterium ' of Ray Lankester, 1 and is really 

 a sulpho-chromogenic bacillus. It occurs 'on the 

 surface of marshes, or on water in which algae are 

 rotting, and sometimes these bacilli are in such 



1 Quarterly Journal of Microscopical Science, vol. xiii. p. 408. 



