44 BACTERIOLOGY 



to believe that there is any more than a remote, or at least 

 superficial, relationship between bacteria and their animal con- 

 geners, the Flagellata. Bacteria are closely related to the 

 lower fission algae, the Cyajiophycea. The Cyanophyceae con- 

 sist of a homogeneous colorless central body, which, according 

 to Hegler, has the structure of a true nucleus and shows indirect 

 karyokinetic division. Surrounding the nucleus is a colored 

 peripheral layer which contains a blue-green ^x^ra^x^'i, phycochrome, 

 consisting of true chlorophyl zxiA phycocyanin, or a modification 

 thereof. Within the latter colored peripheral layer are small 

 granular bodies, cyanophycin grains. Vacuoles also occasionally 

 occur within tlie cells. The cell wall consists of cellulose, and 

 in certain cases may undergo a mucilaginous modification of its 

 outer layer. Endogenous spores are not found, but certain cells 

 have their walls thickened, producing resting bodies or arthro- 

 spores. The Cyanophyceae are not progressively motile, but 

 show only a slow vibratory or rotatory motion due to. an undu- 

 lating membrane. Flagella are not known. From the above 

 description it is seen that the CyanophycecB are distinctly higher 

 structures than the bacteria, in possessing a distinct nucleus, 

 and in the function of carbon assimilation. The greatest 

 morphologic difference lies in the character of the cell wall, 

 which, in the Cyanophyceae, is composed of cellulose and in the 

 bacteria of a proteid body. On the other hand, certain pigmented 

 bacteria approach closely to some of the lower Cyanophyceae ; 

 thus, Bact. viride, B. virens Van Tieghem, and Bact. chlorinum 

 Englemann are tinted a faint green by a substance which, with 

 some doubts, may be regarded as chorophyl. Another class of 

 bacteria studied by Winogradsky contains a red-violet-brownish 

 pigment known as bacteriopurpurin. This latter pigment is easily 

 soluble in absolute alcohol; and, according to Biitschli, if 

 Chromatium. cells be treated with the latter, the violet pigment, 

 bacteriopurpurin, is removed, and there remains a greenish color 

 which is due to chlorophyl, or a related body. Solutions of 



