16 GENERAL MOEPHOLOGY AND BIOLOGY 



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, how- 

 ever, 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. 5). 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 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 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. A leptothrix group is usually 

 described which closely resembles the thiothrix group, except that 

 the protoplasm does not contain sulphur granules. It cannot, 

 however, be with certainty said whether such organisms can be 

 sufficiently differentiated from the bacilli to warrant their being 

 placed among the higher bacteria. In the claEothrisc 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 belong 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 



