VI] GENERAL CHARACTERS OF BACTERIA 103 



division the elements resulting from the division differ in 

 length. 



Spores. — One of the most important and interesting 

 phenomena in the life-history of bacteria is the power of 

 some species to form permanent seeds or spores, by which the 

 species can preserve itself and can withstand a variety of 

 adverse circumstances. Various conditions in nature 

 are often at play, in consequence of which weaker 

 species are less liable to survive in the severe struggle for 

 existence. There is first the adverse circumstance of com- 

 petition, such as constantly obtains under the general con- 

 ditions of growth in soil, in water, and in various organic 

 materials exposed to contamination from air, water, and soil. 

 Here numerous species find access and multiply, some 

 more, others less easily, till all the available nutriment is 

 exhausted. Some species, capable of forming spores, when 

 this stage of the exhaustion of the nutriment has been 

 reached, remain as spores and, till they are transferred by 

 some means or other to new material, or till new nutriment 

 is added, retain their power of again germinating and giving 

 rise to a new crop of the same species, and this survival 

 occurs even under severe adverse circumstances — e.g., the 

 presence of various noxious chemicals, cold, heat, drying, 

 &c. ; but those species that do not form spores retain life 

 only under exceptionally favourable conditions : as a rule, 

 owing to the presence of acids or other chemicals, e.g., 

 products of the growth of bacteria, and owing to drying, &c., 

 they are easily deprived of life. This question of the 

 formation of spores for the above reasons plays a most 

 prominent rok as regards infectious diseases. A few 

 illustrations will easily show this. Take, for instance, the 

 bacillus anthracis. This organism, although present in 

 enormous numbers in the blood and blood-vessels of 



