INTRODUCTION TO IKON-BACTERIA 



155 



cannot call it a real branch, because what has been formed is in 

 reality a new thread which has not yet become completely detached 

 from the parent thread. This peculiar tree-like structure easily 



FIG. 90. Cladothrix dichotoma. 

 (After Zopf.) 



FIG. 91. Cladothrix dichotoma. 

 Portion of thread highly magni- 

 fied. (After Zopf.) 



distinguishes this form from all other bacteria. The average thickness 

 of a thread is about 2 fj.. The sheathing membrane is delicate but 

 clearly visible. Multiplication takes place by the formation of what 

 are known as rod-gonidia. 

 These are the cells inside the 

 sheath which have become 

 rejuvenated : each develops 

 a bundle of cilia (Fig. 92) 

 and, leaving the filament by 

 their aid, swims about for 

 some time, but ultimately 

 settles fast to some object, and 

 then elongates and divides to 

 orm a new thread. An in- 

 teresting feature in connection with this organism is that a pure 

 culture has been obtained by growing it in gelatine and flesh extract. 

 Circular white specks appear in the gelatine-plates, which later become 

 irregular and send out arms in all directions. 



FIG. 92. Cladothrix dichotoma. 



