46 MORPHOLOGY 



ual having produced a new flagellum before separating from the 

 original cell. In the peritrichous bacteria as the cells are elon- 

 gating preparatory to fission, new flagella are developed at the 

 point of constriction between the old flagella. On division be- 

 ing completed, the new flagella come to lie on the end of the cells. 

 Spore Formation. Spore formation, according to various 

 writers, is given as a means of multiplication. The formation 

 of the spore is a means of carrying out one phase of the pro- 

 cess of reproduction. The term " spore " is applied to the rest- 

 ing stages of plant and animal cells. Obviously, the species 

 must be preserved before reproduction and multiplication 

 can take place. The spore has been likened by some to the 

 seed of plants. The spore and the seed serve to carry the 

 parent cells through unfavorable conditions for definite periods 

 in the life history of the organism. Spores are produced by 

 some bacilli and a few spirilla. The first careful study of 

 spores was made by Koch in 1878 in his study of Bacterium 

 anthracis, and by Cohn in his work on Bacillus subtilis. 

 Spore formation usually takes place when the bacterial cell 

 is surrounded by unfavorable conditions, such as exhaustion 

 of the food supply, accumulation of excretory products, ab- 

 normal temperatures, etc. It should be noted in this con- 

 nection that certain protozoan parasites (amoeba) be- 

 come encysted when surrounded by the above-mentioned 

 conditions. A spore will germinate within certain limits of 

 time, when the normal conditions are provided. The first 

 indication of spore formation in a bacterial cell is evidenced 



