GENERAL CHARACTERISTICS OF BACTERIA 



25 



growth may occur only at one end of a filament, the other forming 

 an attachment to some fixed object. (2) The higher forms, moreover, 

 present this further development that in certain cases some of the 

 elements may be set apart for the reproduction of new individuals. 

 The lower fungi have a still more complicate:! development (Fig. 1). 



Morphology. BASK FORMS OF THE LOWER BACTERIA. The basic 

 forms of the single bacterial cells are threefold the sphere, the rod, and 

 the segment of a spiral. Although under different conditions the type 

 form of any one species may vary considerably, yet these three main 

 divisions under similar conditions are permanent; and, so far as we 

 know, it is never possible by any means to bring about changes in the 



EJG. 1 



1, branched filament carrying spores; 2, cross-section of spore highly magnified; 3 and 4, spore 

 building ; 5, developing and bursting spores ; 6and7, branching ; 8, sprouting spores. (After Tavel.) 



organisms that will result in the conversion of the morphology of the 

 members of one group into that of another that is, micrococci always, 

 under suitable conditions, produce micrococci, bacilli produce bacilli, 

 and spirilla produce spirilla. 



The form of the bacterial cells at their stage of complete development 

 must be distinguished from that which they possess just after or just 

 before they have divided. As the spherical cell develops preparatory 

 to its division into two cells it becomes elongated and appears as a 

 short oval rod; at the moment of its division, on the contrary, the trans- 

 verse diameter of each of its two halves is greater than their long 

 diameter. A short rod becomes in the same way, at the moment of 

 its division, two cells, the long diameter of each of which may be 



