THE CLASSIFICATION OF BACTERIA 45 



bacteriopurpurin, according to Lankester, show, when examined 

 with the spectroscope, absorption bands, as in chlorophyl and 

 other cell pigments. Whether certain bacterial cells contain 

 chlorophyl or related bodies with similar physiologic relationships 

 has not been positively decided, but there is reason to believe 

 that such is the case, and that in this is to be found a close 

 relationship between the bacteria and the lower Cyanophyceae. 

 In the highest filamentous Schizomycetes there exist close rela- 

 tionships with the filamentous Cyanophyceae. Thus, Beggiatoa 

 are morphologically quite identical with Oscillatoria, except 

 in the absence of phycocyanin in the former and its presence in 

 the latter. In Beggiatoa rosea-persicina, which contain bacterio- 

 purpurin, the relationship to Oscillatoria is still closer. Equally 

 close relationship exists between Spirochaeta and the fission 

 algae, Spirulina. In the same way Streptothrix is related to 

 Lyngbya or Chamaesiphon ; Cladothrix to Glaucothrix or Toly- 

 pothrix. Crenothrix and Phragmidiothrix, on the other hand, 

 are unique in having no near relatives among the Cyanophyceae. 

 In cell-grouping the analogy between bacteria and the lower 

 algae is a striking one. Thus Streptococci, in the arrangement 

 of the cells, are similar to Anabaena ; Micrococcus has its analogy 

 in Chroococcus, and more especially in the tetrad arrangement 

 of its cells. Micrococcus tetragenus has its prototype in Chroococ- 

 cus turgidus. It has been stated that the cell membrane of bac- 

 teria is a proteid body of indefinite composition, but that it may 

 contain in certain cases, dependent upon the composition of the 

 medium, cellulose or other carbohydrate molecules. Thus Brown 

 believes cellulose to exist in the membrane of Bad. xylinum. 

 From their investigations on Bad. aceti, Nageli and Low con- 

 clude that the cell membrane of that species contains 84 per 

 cent of ash-free cellulose. Similar observations on the presence 

 of cellulose within the capsule have been made by Bovet on the 

 bacterium of Erythema nodusum, and by Hammerschlag on 

 Mycobact. tuberculosis. Thus it is seen that, in the case of cer- 



