112 SULPHUR BACTERIA 



two old threads, of which & is a hollow sheath of hardened 

 slime and containing seven of the objects which may be 

 endospores ; whilst c is a similar thread, but in this the trans- 

 verse bands of hardened slime are also present. It also con- 

 tains one of the objects that may be endospores. 



The plasma is homogeneous, with the sulphur globules 

 and pigment uniformly distributed. In older threads from 

 which the sulphur globules have disappeared a large number of 

 sm^all granules are seen. The nature of these has not been 

 determined. 



Methods of Reproduction. 



(A) Reproduction by fission is the common method. It 

 may take place terminally, or it may be intercalary. Inter- 

 calary grov/th is found only in young threads. In older 

 threads only the tip goes on dividing, and short lengths of the 

 filament arc successively broken off. These are often named 

 " conidia " or " rod-gonidia," which are misnomers, for the 

 difference between such reproduction and fission is one of 

 degree not of kind (see also note on p. 107). In Fig. I2d 

 is shown a young thread in process of liberating a short length 

 from its tip. Connection with the parent thread is still 

 maintained by a band of slime. The same process is in force 

 even when the filament is enveloped by a sheath, for the top 

 of the sheath is open, and the cells are pushed out of the 

 opening by pressure from behind. 



(B) Endospores. — In older filaments a number of bodies 

 are occasionally seen which may be endospores (Fig. 12 h and c). 

 They are roughly cylindrical-elliptical, and approximately 

 of equal size (about 3/^). They were found in old threads 

 of which nothing remained except the sheath. For lack 

 of opportunity, the germination of these structures was not 

 followed so that their spore nature has still to be proved. 



Habitat. — Found in a running stream containing domestic 

 sewage, near Glasgow. 



Note. — The investigation of this organism was unfor- 

 tunately cut short by its disappearance following the intro- 

 duction of sanitary measures, which diverted the course of 

 the sewage. 



