MODES OF REPRODUCTION 



13 



t<^ 





O 



generally at one of the poles, and the spore sprouts like a seed. 

 In the space of about one hour's time the oval refractile cell has 

 become a new bacillus. One spore produces by germination one 

 bacillus. Spores never multiply by fission, nor reproduce themselves. 



Hueppe has stated that there are certain organisms (like 

 Leuconostoc, and some streptococci) which reproduce by the method 

 of arthrospores. Defined shortly, this is simply an enlargement of 

 one or more cell elements in the chain which thus takes on the 

 function of maternity. On either side of the large coccus may be 

 seen the smaller ones, 

 which it is supposed have 

 contributed of their proto- 

 plasm to form a mother 

 cell. An arthrospore is 

 said to be larger, more re- 

 fractile, and more resistant 

 than an ordinary endospore. 

 Many bacteriologists of re- 

 pute have declined hitherto 

 definitely to accept arthro- 

 spore formation as a proved 

 fact. 



Spore formation in bac- 

 teria is not to be considered 



as a method of multipli- ^ ^ "\n '■ 



cation. The general rule ^%(^;^j^jFijy~ Jj^ ^^ ^^ 

 is undoubtedly that one ^ b JJ^ 'h£, ^^ 



bacillus produces one spore, > -^T' 



and one spore germinates fig. 4.-diageams of variods fokms of spobe formation 

 into one bacillus. It is a ^™ ^lagella. 



T ,. , 1 A. stages in formation of spore and its after development. 



reproduction, not a mui- b. Spirlllum with terminal flagella. 



tipUcation. Indeed, the 



whole process is of the nature of a resting stage, and is due {a) to the 

 arrival of the adult bacillus at its biological zenith, or (6) to the con- 

 ditions in which it finds itself being unfavourable to further vegeta- 

 tive growth, and so it endeavours to perpetuate its species. Most 

 authorities are probably of the latter opinion, though there is not a 

 little evidence for the former. Exactly what conditions are favour- 

 able to sporulation is not known. Nutriment has probably an 

 intimate effect upon it. The temperature must not be below 16° C, 

 nor much above 40° C. Oxygen, as we have seen, is favourable, if 

 not necessary, to many species, which will in cultivation in broth 

 rise to the surface and lodge iu the pellicle to form their seeds. 

 Moisture, too, is considered a necessity. 



Koch found that spore formation in B. anthracis occurred in six 



