26 MORPHOLOGY. 



In the following, therefore, where the term spore is used, 

 only endogenous resting forms are to be understood. 



The origin of endospores proceeds similarly, but not 

 identically, in the individual varieties. For the investiga- 

 tion of a certain variety as to spore-formation, as a rule we 

 employ an agar-streak or potato culture, which has been 

 grown at a temperature near the optimum for the variety. 

 After twelve, eighteen, twenty-four, thirty, thirty-six, etc. , 

 hours portions of the unstained culture are examined in 

 water with a narrow diaphragm. If spherical or oval, 

 strongly refracting spores seem to be present, they must be 

 stained according to Neisser or Hauser. (Compare Tech- 

 nical Appendix. ) For the more exact following of spore- 

 formation it is best to place a few bacilli in a drop of gela- 

 tin or agar, and, with the aid of a warming apparatus or 

 in a well- warmed room, to continuously observe and draw 

 definite individuals. 



Motile varieties (according to Fischer) always become 

 quiet before sporulation, yet without shedding their fla- 

 gella. Many varieties grow into longer threads, at first 

 unjoin ted, before spores form. To these latter belongs the 

 anthrax bacillus, whose sporulation will here serve us as a 

 model. (Compare Plate 36, Figs, in and vi.) 



There is first seen a delicate dusty cloudiness in the pre- 

 viously homogeneous bacteria; then, according to Bunge, 

 instead of these finest dust-like particles, a small number 

 of slightly coarser granules appear, which unite among 

 themselves until at regular intervals there lie small round 

 spores (36, vi), which gradually change into the oval, 

 strongly refracting, mature spores (36, in). 



When the spore-formation is complete, there is seen in 

 the thread of bacilli a delicate partition- wall between each 

 two adjacent spores (36, iv). Spores are not matured in 

 all the segments, although the globular precursors may 

 have prepared the way for it. Indeed, some varieties, 

 on account of certain gradually introduced cultural conditions, 

 lose the property of producing mature spores, only 

 physiologically worthless antecedents being formed (Roux, 

 K. B. Lehmann). 



According to Lud. Klein (C. B. vn, 440), spore-formation is quite 

 different in five varieties of anaerobic bacilli, mostly motile, discovered 



