io6 



BACTERIA, YEASTS, AND MOLDS 



One of the rod-shaped forms lengthens itself and divides 

 in the middle and produces two individuals, each of which 

 again lengthens and divides (Fig. 52, b). The same method 

 is found in the spiral bacteria. This manner of division, 

 which is characteristic of all bacteria, will be seen to be 

 quite different from the method we have already noticed 

 in the yeasts. Indeed, the distinction between yeasts and 

 bacteria is based upon this method of multiplication. The 



method of multi- 



-oocooo 



6 



Fig. 52. Showing the method of multiplication 

 by fission, a, a coccus form ; b, a short rod ; 

 c, d, and e, showing the method of growth into 

 long chains and the consequent breaking into 

 sections. 



plication in bac- 

 teria is known as 

 fission, and this 

 group of fungi are 

 called fission fungi 

 in distinction 

 from the yeasts, 

 which are called 

 budding fungi. The 

 difference between 

 these two classes 

 can be distin- 



guished only by careful microscopic study, but it is the 

 scientific distinction between the two groups. 



Spore Formation. Under some circumstances bacteria 

 have a different method of multiplication. Inside of the 

 body of a single individual bacterium appears a little 

 rounded mass which is known as a spore (Fig. 53). This 

 spore may be broader than the rod which produced it, 

 or it may be narrower ; but it finally breaks out, the 

 bacterium itself disappearing and the spore then coming 

 out freely in the medium in which it lives. These 



