PROTOPHFTA. 



249 



Fig. 166. — Schizoraycetes : i Sarcina ; 2 Bacterium ; 

 3 Vibrio; ^Spirillum (after Colin). 



mucilage, and this is especially true of the most minute forms, the investigation of 

 which is hence rendered extremely difficult. 



The forms and vital phenomena of the Schizomycetes, as far as they are accurately 

 known, recall various species of Chroococcaceae and Oscillatorieae ; but they are in 

 general much smaller than the corresponding 

 forms belonging to the chlorophyllaceous 

 series. Thus, for example, Sarcina (Fig. 

 166, i), which grows in the human stomach, 

 corresponds to Merismopedia, the small cells 

 dividing cross-wise and remaining for a time 

 united into tetrads. In the remaining 

 Schizomycetes, which are commonly known 

 as Bacteria, growth takes place only in the 

 direction of length, and the cells formed 

 by repeated transverse division either sepa- 

 rate or remain united into filaments. Gohn 

 divides them into four groups: — i. Sphaaro- 

 bacteria, with extremely small roundish 

 cells which become detached, corresponding 

 to the most minute forms of the Chroococ- 

 caceae and Palmellaceae. They grow on the surface of moist dead organic bodies 

 forming gelatinous growths, often of an intense yellow-green, blue, or violet colour; 

 these pigments which are contained in the protoplasm are sometimes soluble, sometimes 

 insoluble in water. 2. Bacteria proper, in which the cells, when separate, are long, 

 rod-like, very minute, and able to swim about in the fluid. Fluids that contain 

 albuminoids putrefy and become milk-white from the multiplication of these ordinary 

 Bacteria; they correspond in form to the genus Synechococcus among Chroococcaceae 

 which forms bluish-green coatings on rocks ^. 3. Filobacteria, in which the slender 

 cells remain united into threads, which are either straight, forming the genus Bacillus of 

 Cohn, or curved and bent, when they are Vibrio (Fig. 166, 3). They do not excrete 

 a gelatinous envelope and resemble small Oscillatorieae. If the Schizomycetes are 

 constituted into a distinct group, then Beggiatoa, with contractile filaments, which has 

 been hitherto referred to the Oscillatorieae, must be included in it. 4. Spirobacteria, 

 ^"which form spirally curved filaments sometimes of considerable size in comparison to the 

 preceding ones. Cohn distinguishes the genera Spii^illum (Fig. 166, 4) and Spirochcete, 

 which recall Spirulina among the Oscillatorieae. 



D. The Saccharomycetes, of which the genus Saccharomyces is the only one that 

 [is accurately known, consist of small round cells which live isolated, and resemble in 

 form some Chroococcaceae and Palmellaceae ; their organisation is nevertheless capable 

 [of a more accurate investigation than that of the Schizomycetes, which they also usually 

 jreatly exceed in size. The genus Saccharomyces^ which causes the alcoholic fermentation 

 in saccharine fluids, consists of separate cells of an ellipsoidal form with smooth and thin 

 [walls, the protoplasm in which can be clearly recognised as such and encloses one or 

 jmore vacuoles. When growing in a solution capable of fermentation these cells 

 [multiply very rapidly; not however by the ordinary mode of division, but by budding 

 and abstriction. At some point or other of the yeast-cell a small protuberance makes 

 its appearance, which increases to the size of the mother-cell ; the very narrow point of 

 [union then gives way, and the two cells then carry on an independent life, and again 

 repeat the process. Whether under some circumstances the cells can also grow out 



* [E. R. Lankester (Quart. Journ. Micr. Sc. 1873, p. 408) believes, from the investigation of a 

 ich-colouied Bacterium, that the series of forms distinguished by Cohn cannot be maintained as 

 listinct. Lister (ibid. 1873, p. 393) believes that he has demonstrated the origin of Bacteria from 

 a Fungus, a species of Dematiutn.'] 



