CHAPTER X. 



THE INTIMATE STRUCTURE OF THE CELL IN THE 

 SULPHUR BACTERIA. 



Introduction. 



In the Eiibacteria the cell structure of the Bacillus and the 

 Coccus differs essentially from that of the Spirillum. In the 

 first two there is a definite peripheral cell membrane* which can 

 be separated by plasmolysis from the rest of the plasma. The 

 method of division is one characteristic of plant cells. When 

 division takes place, a transverse membrane is formed across 

 the plasma, and separation of the dividing cells is effected by 

 an equatorial fission of this transverse membrane. In the 

 Spirilla, division is effected in a far simpler fashion. The 

 plasma retracts from a zone which extends across the middle 

 of the cell. This appears as a hyaline space, and is occupied 

 by slime. The daughter cells are already organically separated, 

 but are held together by the slime. Complete separation is 

 effected by the two daughter cells pulling in opposite directions, 

 thereby causing the binding slime to stretch out to the point 

 of separation. This method of division is typical rather of 

 the simpler animal cells than of the simpler plant cells. 

 Indeed the genus Spirillum shows more affinities to the animal 

 than to the vegetable kingdom. The distinction may appear 

 to many to justify the separation of the genus Spirillum from 

 the class of Bacteria, but it must be borne in mind that all 

 bacteria are so low in the scale of life that the distinction 

 between an animal and a plant is not so hard and fast as in 

 higher organisms ; and so it is not so inconsistent to place into 



* The membrane in the genus Bacillus is not Ufeless. It is the outer- 

 most, somewhat transformed but Hving layer of the plasma, 



176 



