370 BACTERIOLOOY. 



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 6 and e, Fig. 73.) After forty-eight 

 hours (and frequently sooner) liquefaction of the gelatin 

 has taken place to such an extent that the appearance 

 of the colony is entirely altered. Under the magnify- 

 ing glass the colony proper is now seen to be torn and 

 ragged about its edges, while here and there shreds of 

 the colony can be detected scattered through the liquid 

 into which it is sinking. These shreds evidently 

 represent portions of the colony that became detached 

 from its margin as it gradually sank into the liquefied 

 area. 



At d, in Fig. 73, will be seen a representation of the 

 several appearances afforded by the colonies at this stage. 

 At the end of the second, or during the early part of the 

 third day, the sinking of the colonies into the liquefied 

 pits resulting from their growth is about complete, and 

 under a low lens they now appear as dense, granular 

 masses, surrounded by an area of liquefaction through 

 which can be seen granular prolongations of the colony, 

 usually extending irregularly between the periphery and 

 the central mass. (See e, Fig. 73.) If the periphery be 

 examined, it will be seen to be fringed with delicate, 

 cilia-like lines that radiate from it in much the same 

 way that cilia radiate from the ends of certain columnar 

 epithelial cells. 



These are the more marked phases through which the 

 colonies of this organism pass in their development on 

 gelatin plates. With some cultures the various appear- 

 ances here given appear more quickly, while in cultures 

 from other sources they may be somewhat retarded. 



