114 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



Genus : Amcebobacter Winogradsky. 



The cells are united into colonies, and after division in one direction of space 

 remain attached together by threads of protoplasm. The colonies possess amoeboid 

 motility. The cells change form by contraction and the spreading out of the.proto- 

 plasm. I 



Genus: Thiothece Winogradsky. 



The colonies are inclosed by a thick, gelatinous cyst. The cells are capable of 

 moving and are very loosely surrounded by a common gelatin. 



Genus: Thiodictyon Winogradsky. 



The colonies are solid, non-motile, and consist of small cells which are pressed 

 together. 



V. Subfamily Chromatiaceee. 



The cells are free and capable at all times of motility. 



Genus: Chromatium Perty. 



The cells are moderately thick, elliptical or cylindric-elliptical in shape. 



Genus : Rhabdochromatium Winogradsky. 



The cells are free, rod-shaped, or spindle form; they possess flagella on the 

 poles and are motile at all times. 



Genus: Thiospirillum. 



The cells are free, continually motile, and spirally twisted. 



Relationship of Bacteria* 



There has been a great deal of discussion as to whether bacteria 

 are plants or animals. They were first described as animalcula and 

 to the popular mind they are usually animals or "bugs." It is diffi- 

 cult to determine their exact relation philogenetically. These diffi- 

 culties are so great that some scientists, as Haeckel, would create a 

 new kingdom, call it Protista, and put in it some of the lower plants 

 and' animals which are difficult to classify, together with the bacteria. 

 The bacteria are undoubtedly more closely related to the blue-green algae 

 than to iany other forms of life. They resemble these organisms in form, 

 method of reproduction, and absence of definite nucleus. It is quite 

 impossible to decide, furthermore, whether some forms, such as Bact. viride 

 and Bact. chlorinum, are blue-green algae or bacteria. On the other 

 hand, there are some points of resemblance between the bacteria and 

 the protozoa. Spore formation, similar to that among the bacteria, 

 occurs among some of the protozoa. Another point of resemblance is 

 the possession of flagella. Some of the flagellates quite closely resemble 

 the bacteria in many ways, and the SpirochatcB, which are usually 



• Prepared by W. D. Frost. 



