396 C. CLIFFORD DOBELL. 



PAGE 



Do Bacilhii- Forms with a Yesiciilar Xuclens exist ? . 479 



Yavial>ility of the Xncleiis at Different Periods in the 



Life-cycle ...... 481 



Pleomoi-phism ..... 484 



Do Enucleate Bacteria exist ? . . . . 485 



'• Fusiform Bacteria " . . . 486 



Affinities of Bacteria ..... 487 



Conclusions ...... 488 



Appendix: On thk Alleged Al-togamt of Bacteria . 489 



LlTEKATURE ...... 492 



Explanation of Plates .... 499 



" Ich hoffe zuversichtlich, class wir nicht nielir allzu weit von dem 

 Augenblicke entfernt sind, wann es klar werden wird, dass die verschie- 

 denavtigsten Angaben. insofern dieselben einer ernsteu und gewissen- 

 haften wissenschaftlichen Arbeit entspringen. alle in reinen Einklang 

 gebracht wei'den, so dass eiii iienes schones Gebaude, das der Bacterien- 

 cytologie, in der allerfeinsteu der Wissenschaften hoch emporragen 

 wird."— Mencl (1910). 



INTRODUCTION. 



It is a remarkable fact that modern cytologv, -wliicli lias 

 recently made such rapid strides as the result of the enthu- 

 siastic investigations of a vast array of workers,, has almost 

 lost sight of the liacteria. Cytologists and pi-otistologists 

 alike liave been content, for the most part, with assuming that 

 the Bacteria are a group of simple organisms, possessing but 

 Httle structural differentiatiou, and have then left them alone. 

 Yet no biologist would deny, I think, that it is of the utmost 

 importance that we should possess exact detailed knowledge 

 of the structure and life-history of this immense group of 

 living beings. More than one of the current conceptions in 

 biology must undergo profound modification when Ave have 

 precise information regarding the Bacteria. 



If anyone endeavours, at the present moment, to ascertain 

 from the vast bacteriological literature, which has been 

 pouring out for many years past, the present state of know- 

 ledge regai'ding the structure of Bactei'ia, he will find that the 

 whole matter is in a state of utter chaos. He will find that 



