MORPHOLOGY AND BIOLOGY. 253 



In gelatin plates colonies appear within twenty-four hours 

 (Figs. 104 and 107). They are very small, granular, with irreg- 

 ular borders, of a whitish color, and develop in the medium. 



FIG. 107. FIG. 108. 



Cholera colonies in gelatin : twenty-four Cholera colonies in gelatin : thirty- 

 hours' growth. (Dunham.) six to forty-eight hours' growth. X 



about 30. (Park.) 



These colonies gradually turn from white to yellow and from 

 yellow to brown, at the same time liquefying the gelatin quite 

 rapidly until each colony occupies a small conical depression. 

 The old colonies are very granular and glistening (Fig. 108). 



FIG. 109. 



Cholera colony in gelatin. X 30. (Dunham.) 



Their appearance at this time is that of a dirty granular mass 

 strewn with small bits of glass. Each colony is surrounded 

 by a transparent halo (Fig. 109). The colony gradually sinks 



