THE HIGHER BACTERIA. 19 



attaching the organism to some other object. The greatest 

 advance, however, consists in the setting apart among most 

 of the higher bacteria of the free terminations of the 

 filaments for the production of new individuals. The 

 protoplasm then undergoes special changes, whereby small 

 rod-shaped forms (differing often in appearance from the 

 elements of which the filament is composed) are produced. 

 These are often called conidia ; they are often motile, and it 

 is from them that new individuals are developed. There 

 are various classes under which the species of the higher 

 bacteria are grouped ; but our knowledge of them is still 

 somewhat limited, as many of its members have not yet 

 been artificially cultivated. The beggiatoa group consists 

 of free swimming forms, motile by undulating contractions 

 of their protoplasm. For the demonstration of the rod- 

 like elements of the filaments special staining is necessary. 

 The filaments have no special sheath, and the protoplasm 

 contains sulphur granules. The method of reproduction is 

 doubtful. The thiothrix group resembles the last in structure, 

 and the protoplasm also contains sulphur granules ; but the 

 filaments are attached at one end, and at the other form 

 conidia. The kptothrix group resembles closely the thio- 

 thrix group, but the protoplasm does not contain sulphur 

 granules. In the cfadotkrix group there is the appearance 

 of branching, which, however, is of a false kind. What 

 happens is that a terminal cell divides. It divides again, 

 and pushes the product of its first division to one side. 

 There are thus two terminal cells lying side by side, and 

 as each goes on dividing, the appearance of branching is 

 given. Here, again, there is conidium formation ; and while 

 the parent organism is in some of its elements motile, the 

 conidia move by means of flagella. The highest develop- 

 ment is in the streptothrix group, to which belongs the 

 streptothrix actinomyces, or the actinomyces bovis, an 

 important pathogenic agent. Here the organism consists 

 of a felted mass of non-septate filaments, in which true 

 dichotomous branching occurs. Under certain circum- 

 stances threads grow out, and produce chains of coccus- 



