MICROSPIRA COMMA. 



477 



mately assumes the appearance of a dense, white mass 

 lying at the bottom of a sharply-cut pit or funnel con- 

 taining transparent fluid. This liquefaction is never 

 very widespread nor rapid, and rarely extends more 

 than one millimetre beyond the colony proper. On 

 plates containing few colonies there is little or no 

 tendency for them to become confluent, and they rarely 

 exceed 2 to 3 mm. in diameter. 



FIG. 76. 



Developmental phases of colonies of microspira comma at 20 to 22 C. on 



gelatin. X about 75 diameters 



a. After sixteen to eighteen hours. 6. After twenty-four to twenty-six 

 hours, c. After thirty-eight to forty hours, d. After forty-eight to fifty 

 hours, e. After sixty-fonr to seventy hours. 



When examined under a low magnifying lens the very 

 young colonies (sixteen to eighteen hours old) appear 

 as pale, translucent, granular globules of a very delicate 

 greenish or yellowish-green color, sharply outlined, and 

 not perfectly round. (See a, Fig. 76.) As growth pro- 

 gresses this homogeneous granular appearance is re- 

 placed by an irregular lobulation, and ultimately the 

 sharply-cut margin of the colony becomes dentated or 

 scalloped. (See b and c, Fig. TQ.) After forty-eight 

 hours (and frequently sooner) liquefaction of the gelatin 



