16 GENERAL MORPHOLOGY AND BIOLOGY 



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 cladothrix group 

 there is the appearance of branching, which, however, is of a 

 false kind. Whaf 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 reaction's nor resisting powers 

 of so high a degree as ordinary bacterial spores. Sometimes, too, 

 the protoplasm of the filaments breaks up into bacillus-like 

 elements, which may also have the capacity of originating new 

 individuals. In the streptothrix actinomyces there may appear 

 a club-shaped swelling of the membrane at the end of the fila- 

 ment, which has by some been looked on as an organ of 

 fructification, but which is most probably a product of a 

 degenerative change. The streptothrix group, though its 

 morphology and relationships are much disputed, may be looked 

 on as a link between the bacteria on the one hand, and the 

 lower fungi on the other. Like the latter, the streptothrix forms 

 show the felted mass of non-septate branching filaments, which 

 is usually called a mycelium. On the other hand, the breaking 



