CLASSIFICATION OF THE BACTERIA 23 



the protoplasm at the point where the spore is to form 

 becomes more dense and finally surrounds itself by a definite 

 membrane or membranes. A mother cell containing a spore 

 is sometimes termed a sporangium. The spore differs from 

 the cell in which it is produced usually by beiri somewhat 

 smaller, by having a much firmer membrane, and by its 

 lower water content. It is usually well fitted to survive 

 unfavorable conditions for a considerable period of time. 

 In most cases the spore mother cell wall eventually breaks 

 away leaving the spore free. 



Usually each species of spore-producing bacillus has its 

 own characteristic shape, size, and position for the spore. 

 These spores may be located either at the center or at or 

 near the end of a cell. In some species in which the spore 

 is located near the equator the mother cell wall bulges, 

 making the cell spindle-shaped. Such an organism is some- 

 times termed a clostridium. In other cases the spore does 

 not cause such cell enlargement. A few species of bacteria 

 produce spores at the end of the cell, causing considerable 

 enlargement. Such a drumstick-shaped cell is sometimes 

 termed a plectridium. 



When spores come under favorable conditions for de- 

 velopment they will germinate, producing rods similar to 

 those from which they originated. These rods will then 

 go on multiplying by fission until stimulated in some way 

 themselves to produce spores. The stimulation to spore 

 production is not necessarily unfavorable conditions for 

 growth as is ordinarily understood. In other words, al- 

 though spores undoubtedly serve the purpose of tiding 

 bacteria over unfavorable conditions, the organism does not 

 need to be subjected to these unfavorable conditions before 

 producing spores. It appears to be quite as much a part of 

 the regular life cycle of some bacteria to produce spores as 

 it is a part of the regular life cycle of the corn plant to 

 produce an ear of corn. 



