186 GENERAL HISTOtlY OF THE INFUSORIA. 



lineola, whilst Dujardin more correctly separated it from the Vibrios under 

 the name of Bacterium Teryno. Under this latter appellation Perty has also 

 described it. 



Now when we come to examine an infusion rich in these organisms, nu- 

 merous jelly-like colourless masses of different size and figure (XVIII. 69) 

 may be met with on the waUs of the vessel, and on the surface of the fluid. 

 These when young resemble small balls, fi^om 1-100'" and less in diameter; 

 but as they continue constantly to enlarge, they acquii-e a clustered outline, 

 and exhibit themselves as colourless masses and films of very considerable 

 superficial dimensions and thickness, resembling soft Palmellse in consistence. 

 Like these they are composed of a transparent mucus, in which numberless 

 punctate or linear corpuscles are imbedded. These last are identical with 

 the isolated particles known as Bacterium Termo. That these corpuscles are 

 held together by the common mucus, is evident to the eye ; even the largest 

 films are also composed of globular clusters agglomerated together, the out- 

 line of the gelatinous mass appearing sharply defined in the water. More- 

 over, the linear corpuscles appear more thickly congregated at the periphery 

 than in the centre of the spherical collections ; but this is an optical delusion. 

 Again, when coloiu'ing matter is added to the water, the Bacterium-TmiQ.ws> is 

 not tinged by it ; and when any passing Infusorium impinges against it, its 

 surface is pressed in ; and lastly, the absence of an independent and inherent 

 molecular motion among the particles show them to be enclosed within a re- 

 sistant medium. Frequently, whilst under observation, single corpuscles may 

 be seen to detach themselves and swim away in the characteristic manner. 



The definite outline and figure of the mucilaginous globules, and of their 

 clusters, refute the notion that such are merely collections of dead Bacterium- 

 corpuscles. The indication is rather that the Pahnella-V^^e masses represent 

 the young condition of Bacterium; indeed, the same cycle of development 

 proceeds as in PahneUa, Tetraspora, and allied forms .... The only difference 

 betwixt the J5ac^^rn«)i-heaps and Palmella- or Tetraspora-va^^^Q^ is, that in 

 the first the individual corpuscles are so minute that the characters of simple 

 cells cannot confidently be assigned them, and that, instead of being yellow 

 or light green, they are quite coloui4ess. Nevertheless, in Kiitzing's Palmella 

 Brehissonii and P. hyalhia, the cells are only 1-3000 to 1-1000'" in length, 

 whilst their figure and distribution are indistinguishable from Bacterium. The 

 absence of colour is a feature of the Pungi connected with their occiuTence 

 in decomposing infusions ; yet Palmella hyalina has only a pale ochreous hue, 

 and Cohn seems to satisfactorily establish that the mere presence or absence 

 of coloiu' cannot constitute that decisive character which the separation of 

 the microscopic Fungi from the Alg^e implies. 



From the above it appears evident that the corpuscles known as Bacterium 

 Termo are the swarm-cells (zoospores) of a plant aUied to Palmella and Te- 

 traspora, but referable, by reason of the want of coloui% to the microscopical 

 aquatic Fungi. When these Vibrios pass into a state of rest, they accumu- 

 late on the sm^ace of the water in the form of films, &c., as do the resting- 

 spores of Tetraspora, Stigeoclinium, Conferva, and other Algse, but, unHke 

 these, are connected together by an intercellular substance, within which 

 their growth proceeds, and leads frequently, as Perty has illustrated, to theu' 

 disposal in linear branching series. 



From the analogy mth Tetraspora and the other swarm-cells of Algee and 

 Fungi, it must be assumed that the Bacterium-corpuscles move by means of 

 a vibratile fibre ; indeed Ehrenberg intimates having seen a filament in 

 Bacterium triloculare, and Dujardin considered some such mechanism pro- 

 bable. 



