18 POSITION— RELA T ION SHI PS 



If certain aspects of chemical composition are considered, 

 all organisms are found to be alike since all contain the same 

 twelve elements-C, H, O, N, S, P, CI, K, Ca, Mg, Fe, Mn- 

 and the same classes of compounds, namely, proteins, carbo- 

 hydrates, fats, mineral salts and water. 



In attempting to place the bacteria with their nearest 

 relations they must be compared with other protista in all 

 the characteristics mentioned in the paragraphs above. 



Morphology.— Bacteria look most like the lowest algse, the 

 blue-green algse. A study of Figs. 1 to 7 will show that the 

 forms of the cell are very similar and that the cells are 

 grouped in similar ways. The grouping of the cells shown is 

 the result of their dividing and remaining attached and 

 indicates that both these algse and the bacteria reproduce the 

 same way, that is, by simple transverse division. Bacteria 

 are not considered to be algse because of a fundamental 

 difference in metabolism due to the fact that alga^ show a 

 marked difference in chemical composition. They contain 

 chlorophyl and bacteria do not. Chlorophyl is the green- 

 coloring matter which is considered to enable organisms 

 possessing it to utilize sunlight to split up carbon dioxide and 

 build up organic compounds from it.^ Bacteria with few 

 exceptions (see Chapter VII) are dependent on complex 

 carbon compounds for their carbon and cannot utilize CO2. 



Physiology— Metabolism.— In metabolism the bacteria most 

 closely resemble the fungous or non-chlorophyl plants 

 especially the yeasts and molds. Their chemical composition 

 is also nearest to that of these forms. Another argument for 

 relationship of bacteria to the yeasts is that there are certain 

 organisms which appear to be intermediate between them, 

 transition forms, the Schizosaccharom/ycetes, or fission yeasts. 

 Fig. 9. Such connecting links are good evidence of relationship. 



Bacteria are not yeasts nor are they molds. They differ 

 from both in their manner of reproduction. Bacteria, as has 

 been stated, reproduce by simple transverse division. Yeasts 

 reproduce by budding or gemmation and also by spore 

 formation . The fission yeasts produce spores like the yeasts 

 do and also divide transversely like the bacteria. Molds 



1 See Photosynthesis: Prof. E. C. C. Baly, Science, 1928, 48, 364. 



