1878.] 



the Life-History of Spirillum. 



483 



often unequal in size (fig. 6). Such irregularity of division very 

 often also takes place outside the filaments (fig. 14). 



When naturally sown in the glcea, in the way above described, the 

 spores encapsulate themselves, and very often, if not always, divide 

 into two or more sporules (fig. 8a). The capsules may remain 

 isolated or also divide, forming patches of two or three (fig. 86), 

 or along with others, uniting into large irregularly cohering masses 

 (fig. 13c). Sometimes, also, many may be enclosed in a definite 

 cellulose envelope (fig. 8d) ; this last perhaps arising, like a colony 

 of Gloeocapsa, from the division of a single spore. When old, the 

 capsules may lose their pale blue colour, and even become suffused 

 with dingy brown. 



The sporules may either desert the capsules (fig. 8e), leaving 

 vacuoles, as in the ripe filaments, such empty capsules being found in 

 great numbers ; or may cause them to become actively motile, their 

 motion being either corkscrew- like or direct without revolution ; in 

 the former case resembling a Spirillum, in the latter a monad. On 

 escaping from the capsule, the sporules appear generally to rise to the 

 surface, forming large dark granular masses (fig. 10). 



A nutritive fluid, prepared by boiling a piece of zoogloea in some 

 water taken fron the aquarium, was inoculated with these surface 

 sporules and placed on the warm stage. Twenty-four hours after, 

 many of the brown sporules were sending out a small curved hypha, 

 at first slightly tinged, while later, distinct " commas," and even 

 young Spirilla, were developed. 



It is of great interest that we occasionally found a large, very finely 

 granular sphere of the characteristic colour (fig. 9), while smaller and 

 coarser masses were more abundant (fig. 9b), affording a transition to 

 the common sporule cyst. These correspond to the smaller " macro- 

 plasts " figured by Lankester,* in his Bacterium rubescens, and to 

 the finely granular colourless spheres, figured by one of us in the 

 preceding paperf from a species of Bacillus. These probably result, as 

 in Bacillus, from the long-continued subdivision of a single spore or 

 sporule. 



The division of the spores inside and outside the filaments is of 

 great interest, and goes far to prove the unspecialised and Protean 

 nature of Bacterial forms, almost all possible modes of division being 

 found in the same field. Some divide transversely into two equal 

 parts, others bud like Torulai, others again lengthen into rod-like 

 and Vibrio-like forms, and then break up into three or four portions 

 (figs. 13 and 14). 



The life-history of Spirillum, so far as we at present know, may be 

 thus summarised. The well-known motile corkscrew may alternate 



* " Quart. Journ. Micr. Sci.," vol. xvi, Plate 3. 

 f Plate 10, Series IV, e f g. 



