SPORE FORMATION 5 



ami size is quite lost. The appearance of the protoplasm 

 also is often altered. Instead of, as formerly, staining well, it 

 does not stain readily, and may have a uniformly pale homo- 

 geneous appearance, while in an old culture only a small 

 proportion of the bacteria may stain at all. Sometimes, on the 

 other hand, a degenerated bacterium contains intensely stained 

 irrannlt's or globules which may be of large size. Such aberrant 

 ;nil degenerate appearances are referred to as involution forms. 

 That these forms really betoken degenerative changes is shown 

 by the fact that, on their being again transferred to favourable 

 conditions, only slight growth at first takes place. Many 

 individuals have undoubtedly died, and the remainder which 

 live and develop into typical forms may sometimes have lost 

 some of their properties. 



Reproduction among the Higher Bacteria. Most of the higher bacteria 

 consist of thread-like structures more or less septate and often surrounded 

 by a sheath. The organism is frequently attached at one end to some 

 object or to another individual. It grows to a certain length and then 

 at tin' lice end certain cells, called gonidia, are cast oil' from which new 

 individuals are formed. These gonidia may be formed by a division 

 taking place in the terminal element of the filament such as has occurred 

 in the growth of the latter. In some cases, however, division takes 

 j'lai ( in three dimensions of space. The gonidia have a free existence 

 fur a certain time before becoming attached, and in this stage are 

 sometimes motile. They are usually rod-like in shape, sometimes 

 pyriform. They do not possess any special powers of resistance. 



Spore Forma,tion. In certain species of the lower bacteria, 

 under certain circumstances, changes take place in the protoplasm 

 which result in the formation of bodies called spores, to which 

 the vital activities of the original bacteria are transferred. 

 Spore formation occurs chiefly among the bacilli and in some 

 spirilla. Its commencement in a bacterium is indicated by the 

 appearance in the protoplasm of a minute highly refractile 

 granule unstained by the ordinary methods. This increases in 

 -i/i-, and assumes a round, oval, or short rod-shaped form, always 

 shorter but often broader than the original bacterium. In the 

 process of spore formation the rest of the bacterial protoplasm 

 may remain unchanged in appearance and staining power for a 

 considerable time (e.g. b. tetani), or, on the other hand, it may 

 soon lose its power of staining and ultimately disappear, leaving 

 the spoiv in the remains of the envelope (?.</. b. anthracis). 

 This method of spore formation is called cn<l<><i< nuns. Bacterial 

 spores are always non-motile. The spore may appear in the 

 centre of the bacterium, or it may be at one extremity, or a 

 short distance from one extremity (Fig. 1, No. 11). In structure 



