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 ' endospore ' 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 



tit 



FIG 



spore 



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

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

 c and d, Clostridium butyricum (Prazm.) : 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^/l Plectridium paludpsum : e, unchanged 

 rod ; _/J drum-stick or tadpole form with ripe spore in swollen end. f, Germination of spore in B, anthracis ; the 

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



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

 in anthrax, separates from the spore membrane (6) (from Prazmowski). * 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-f about 1200, g-i 1000. 



(Fig. ii, 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, h, i}. The spores of 



B. subtilis 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 



