SPORES OF BACTERIA. 



195 



102. The Mother-of- 

 Vinegar. The edge of a 

 film of zoogloea of mother- 

 of-vinegar as it appears 

 under a high power. The 

 bacteria are seen imbedded 

 in the jelly which they 

 have secreted. 



withdraw from the wall and condense into a (usually oval) 



mass at one end of the cell, leaving the rest of it empty 



It is at this time that the cell- wall 



is best seen. The condensed mass 



now becomes dark and opaque, appa- 



rently from the deposit upon itself of a 



greatly thickened and peculiar wall; it 



refuses to absorb stains which the origi- 



nal cell would have taken, and becomes 



exceedingly resistant to extremes of 



heat, cold, and dryness (Fig. 105). To FlG 



these spores the Germans give the 



excellent term Dauersporen, i.e., 



enduring 

 spores^ 

 often called 



resting spores. AYhen brought under 

 favorable conditions, these sprout 

 and, the ordinary bacterium cell 

 having been produced, growth and 

 fission proceed as before. Obviously 

 these spores are very different in 

 function from those of Pteris (p. 

 130), since they are protective 

 merely, and not reproductive. They 

 correspond, doubtless, to that phase 

 of animal life which is known as the 

 ' ' encysted ' ' state. Another mode 



/ 



of spore-formation in bacteria is that 

 known as the production of arthro- 

 spores, in which a long slender cell 

 may become constricted and detach 

 daughter-cells from one or both ends. 

 This is obviously a. special case of 

 FIG. los.-ciiiated Bacteria. The unequal cell-division, but if it exists 



bacillus of typhoid fever, showing n / i i i i j i ^ i\ * 



cilia. (From a specimen prepared *t all (which has been doubted) it 



by s. c. Keith, jr. Drawn by j. H. clearly approaches again ogenesis 



Emerton.) 



. i r 



in such forms as 



Physiology. Income, Metabolism, and Outgo. The bacteria 



