7O CULTURES OF BACTERIA. 
7, Allow to develop as directed for tube cultures, 
and examine from day to day, or oftener as necessary. 
8. In plate cultures note : 
(a) Is there a difference in the number of colonies 
in the three dishes? ‘The use of the three tubes 
and plates is for the purpose of reducing the num- 
ber of colonies, so that only a few will be present 
in the third plate. 
(4) Is there more than one kind of colony present ? 
Notice that colonies on the surface differ from 
those below the surface, though of the same species. 
If the culture from which the inoculations were 
made is a pure culture, and if no germs have been 
allowed to enter during the process of making the 
plates, there should be but one kind of colony present. 
(c) What are the size, shape, texture, and color 
of the colonies, both surface and deep? What is 
the character of their margins? 
The following terms are those suggested by 
Chester for the description of colonies : 
I. Form. 
Punctiform, dimensions too small for defini- 
tion. 
Round, of a more or less circular outline. 
Lrregular. 
Elliptical. 
Fustform, spindle-shaped. 
Cochleate, spiral or twisted like a shell. 
Amebord, very irregular, streaming. 
Mycelioid, a filamentous colony with the 
radiate character of a mould. 
