1 III.] 



A rthrosporous Bacteria. 



into a coil ; in the fluid short and motionless filaments are 

 formed only at a temperature of more than 35 C. ; at 20 C. the 

 filaments separate into motile rods. At the close of their vege- 

 tation when the substratum is exhausted, the rods fall asunder 



Fig. 3- 



into short roundish cells, and these again may be termed spores 

 since in a fresh substratum they develope into new rods or 

 filaments. 



Though their course of development is more complex yet the 

 phenomena observed in Crenothrix, Cladothrix, and Beggiatoa, 

 if ZopPs description is correct, closely resemble those just de- 

 scribed. They will be noticed again below in Lecture VIII. 



Fig. 3. Leuconostoc mesenterioides, Cienkowski. a sketch of a Zoogloea. 

 b section through a full-grown Zoogloea just before the commencement of 

 spore-formation, c filaments with spores from an older specimen. 

 d isolated ripe spores, e-i successive products of germination of spores 

 sown in a nutrient solution ; sequence of development according to the 

 letters. In e the two lower specimens show the fragments of the ruptured 

 spore-membrane on the outer surface of the gelatinous envelope indicated by 

 dark strokes, i portion of a gelatinous body from h broken up into short 

 members, which have been separated from one another by pressure. After van 

 Tieghem (Ann. d. sc. nat. ser. 6, vii). a natural size, b-i magn. 520 times. 



