20 



MORPHOLOGY 



period, for months or years. It has, however, the ability to enter into a 

 resting stage, to assume a shape endowed with great powers of resistance 

 the ' spore.' This power it shares with all low organisms such as algae or 

 fungi, which are periodically subject to dearth of nutriment or the inclemency 

 of the seasons. The term 'spore' is commonly applied to all these resting 

 forms, but must not be supposed to connote anything but a similarity of 

 function. The word ' cndospore ' has in addition a special morphological 

 significance, and is applied to the commonest form of bacterial spores. 

 Taking the sporulation of the anthrax bacillus as a type, we find the 

 process begins by a contraction of the cell-contents, which ball themselves 

 together into an egg-shaped mass as yet devoid of a proper membrane, 

 and lying loose in the otherwise empty rodlet : this is the young spore 



FIG. ii. Sporulation and germination, a, Anthrax bacillus with the cell-contents contracted to form the young 

 spore, as yet without membrane ; 6, ripe anthrax spore still enclosed in the rod, whose shape has not changed. 

 c and d, Clostridium bnt\ricitm (I'razm.) : c, vegetative peritrichous stage ; d, ripe spore in the swollen spindle-shaped 

 cell, the contents of which are not quite used up in spore-formation, e and/; Plectridiiim palitdositm : e, unchanged 

 rod ; f, drum-stick or tadpole form with ripe spore in swollen end. jr, Germination of spore in B. antliracis\ the 

 young rod elongates itself in a direction parallel to the longer axis ofthe ellipsoidal spore (3, 4) (from Prazmowski). 

 A, Germination of spore of B. subtilis\ the new rod grows out at right angles to the axis ofthe spore (3-5), and, as 

 in anthrax, separates from the spore membrane 16) (from Prazmowski). i B. leptosporus ; the spore, surrounded 

 by a thin mucous coat (dotted 1-3), grows out into a rod without shedding a membrane; simplest form of germina- 

 tion (from Klein). Magn. a 2250, b-j about 1200, g-t 1000. 



(Fig. n, a]. This contracts still further, becoming denser and more highly 

 refractive than when it filled out the cell, and there forms upon its surface 

 a firm coat, the proper spore-membrane, to the impermeability of which the 

 durability and resistance of the spore are due. The spore lies now complete 

 within the cell- wall (Fig. 1 1, b], which gradually decays and sets it free. The 

 free spore, which may be found abundantly in cultures two to three days old, 

 is a highly refracting, ellipsoidal, immobile body, considerably smaller than 

 the cell in which it arose. Under favourable conditions of temperature it 

 germinates in twenty-four to thirty-six hours. Rags of the cell-membrane 

 may often be seen still adhering to it (Fig. n, g, Ji, i). The spores of 

 B. siibtilis are formed in a like manner, the rods, as in B. anthracis, retaining 

 their cylindrical shape during the process (Figs, n, b ; 13, c]. A less simple 

 type of sporulation is that where the rods change their shape, becoming 



