M feACfERlA. 



of the cell, which, only as it degenerates or dies, leaves the 

 resting-spore free to be carried about from place to place 'by 

 currents of air or water, to be developed when the conditions 

 of moisture, temperature, and food supply again become suffi- 

 ciently favourable. Where the diameteS: of the spore exceeds 

 that of the bacterium, it may be situated in the centre, giving 

 rise to a spindle-shaped organism, or it may be at one end, 

 when the organism becomes clubbed or pendulum-shaped. 

 The spore in this case appears to escape more readily, and 

 before the complete disintegration of the bacterium has taken 

 place ; the side or end of the swollen organism gives way and 

 allows of the spore being set free. This is only one kind of 

 spore formation, and is spoken of by De Bary as endospore 

 formation. It is met with in some varieties of vibriones, in 

 many of the bacilli and in certain of the spirilla (Co'rnil 

 and Babes) ; whilst Zopf describes similar spore formation as 

 occurring in certain micrococci, and Escherich points out 

 that he obtained undoubted spores in sarcina pulmonum, 

 I.e., bodies that admitted of double staining. 



A second kind of spore, to which is given the name of 

 Arthrospore, is also described by De Bafy, Hueppe and 

 others. In this there is a combination of spore formation 

 and of fission ; the mother-cell undergoes division into a series 

 of daughter-cells, a few of which differ from the rest in very 

 important . and essential points. There appear to be two 

 kinds of arthrospores ; one form, met with in Leuconostoc, 

 for example, where simple vegetative division of small round 

 bacteria goes on regularly, so long as the conditions are 

 favourable, and a regular chain is formed. In this chain 

 there appear at intervals, micrococci, which differ from the 

 remainder of the elements of the chain in the following 

 points : As soon as the conditions of nutrition are altered 

 they do not, like the other parts of the chain, die off, 

 but they become "somewhat larger than the rest, acquire 

 a more distinct outline, become thicker-walled, and their 

 protoplasm grows darker. Eventually they become free by 

 the deliquescence of the gelatinous envelopes, and may 

 claim the name of spores, because, when placed in the fresh 

 nutrient solution, they develop into new rows of beads like 

 those of the mother plant." Here is a body which has most 

 of the characteristics of the resting-spore or seed, but it is not 

 formed within the protoplasm of the vegetative organism, 



