THE HIGHER BACTERIA 15 



most cases the filaments at more or less regular intervals are cut 

 by septa into short rod-shaped or curved elements. Such 

 elements are more or less interdependent on one another, and 

 special staining methods are often necessary to demonstrate the 

 septa which demarcate the individuals of a filament. There is 

 further often a definite membrane or sheath common to all the 

 elements in a filament. Not only, however, is there this close 

 organic relationship between the elements of the higher bacteria, 

 but there is also interdependence of function ; for example, one 

 end of a filament is frequently concerned merely in 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 produc- 

 tion of new individuals, as has been described (p. 2). 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 the members have not yet been artificially 

 cultivated. The hggcizatoa 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 re- 

 sembles the last in structure, and the protoplasm also contains 

 sulphur granules; but the filaments are attached at one end, 

 and at the other form gonidia. The leptothrix group resembles 

 closely the thiothrix group, but the protoplasm does not contain 

 sulphur granules. In the cladothrix group there is the appearance 

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

 is that a terminal cell divides, and on dividing again, it 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 

 gonidium formation ; and while the parent organism is in some 

 of its elements motile, the gonidia move by means of flagella. 

 The highest development is in the streptothrix group, to which 

 belongs the streptothrix actinomyces, or the actinomyces bovis, and 

 several other important pathogenic agents. Here the organism 

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

 dichotomous branching occurs. Under certain circumstances 

 threads grow out, and produce chains of coccus-like bodies from 

 which new individuals can be reproduced. Such bodies are often 

 referred to as spores, but they have not the same staining reactions 

 nor resisting powers of so high a degree as ordinary bacterial 



