MORPHOLOGY. 41 



under special conditions — certain of them possessing the 

 power of forming spores, while from others this pecu- 

 liarity is absent. >^ 



, As yet but little is known of the life history of the 

 spiral forms. Efforts toward their cultivation under 

 artificial conditions have thus far been successful in 

 only a few cases. Morphologically, they are thread- 

 or rod-like bodies which are twisted into the form of 

 spirals. In some of them the turns of the spiral are 

 long, in others quite short. They are motile, and 

 multiply apparently by the simple process of fission.' 



The micrococci develop by simple fission. When 

 development is in progress a single cell will be seen to 

 elongate slightly in one of its diameters. Over the 

 centre of the long axis thus formed will appear a slight 

 indentation in the outer envelope of the cell ; this 

 indentation will increase in extent until there exist 

 eventually two individuals which are distinctly spheri- 

 cal, as was the parent from which they sprang, or they 

 will remain together for a time as diplococci. The sur- 

 faces now in juxtaposition are, flattened against one 

 another, and not infrequently a fine, pale dividing line 

 may be seen between the two cells. (See Fig. 1, c and 

 d.) A similar division in the other direction will 

 now result in the formation of a group of forms as 

 tetrads. 



V In the formation of staphylococci such division occurs 

 irregularly in all directions, resulting in the produc- 

 tion of the clusters in which these organs are com- 

 monly seen. (See Fig. 1, a). With the streptococci, 

 however, the tendency is for the segmentation to con- 

 tinue in one direction only, resulting in the production 



1 Dividing Into two transversely. 



