THE GENUS SPIROCHETA AND ALLIES 221 



nucleus like that of most protozoa and higher types of cell. Nor do 

 the granules collect in spore aggregates, such as Schaudinn ('02) 

 described in Bacillus biitschlii and Guilliermond ('08) in different 

 endosporous bacteria. The nuclear apparatus is of the "diffuse" 

 type, therefore, and represents an intermediate condition between the 

 "distributed nucleus" of bacteria and the morphological nucleus of 

 higher cells. 



The protoplasmic body is covered by a distinct sheath or periplast, 

 which is twisted in a characteristic manner and which gives rise to a 

 lateral undulating membrane likewise spirally wound and running 

 from end to end of the organism (Figs. 87, 88). Laveran and Mesnil 

 regard this membrane as a mere fold of the periplast (gaine) and of an 

 accidental nature, but both Perrin and Fantham give sufficient evi- 

 dence to show that it is a definite organoid of the cell, while Fantham 

 has demonstrated the presence of numerous fibrils which he describes 

 as myonemes and correctly interprets as the seat of movement of 

 the cell (Fig. 88, A,C}. Under abnormal conditions, the membrane, 

 like that of the ciliated infusoria, may disintegrate, and the several 

 myonemes then may assume the appearance of numerous flagella, 

 a phenomenon which may account for the presence of many flagella 

 occasionally found on Spirocheta gallinarum and Spirocheta duttoni. 

 The movements brought about by this membrane are characteristic 

 of spirochetes in general, and consist of rotation about the long axis, 

 forward or backward translation, and bending movements at different 

 levels of the body, all of which may occur simultaneously or inde- 

 pendently. 



Reproduction occurs by either longitudinal or transverse division. 

 There is some difference of opinion in regard to the mode of division, 

 however. Laveran, Mesnil, and Swellengrebel maintain that it is 

 always transverse; Perrin, that it is always longitudinal; while Certes, 

 Lustrac, and especially Fantham, whose account is the most con- 

 vincing, found both types, cross-division more rarely than lengthwise. 

 Transverse division, according to Swellengrebel, occurs, as in bacteria, 

 by the preliminary division of internal granules and by the forma- 

 tion of a "cloison transversal," but he also figures and describes the 

 double chromatin granules which can be interpreted only as a prepa- 

 ration for longitudinal division. Longitudinal division, according to 

 Fantham, begins with division of the membrane, being first noted in 

 the division of what he terms the basal granules (Fig. 88, E). The 

 granules at one end separate while the others remain together, and with 

 the separation the membrane, chromatin granules, and cell divide, the 

 daughter cells remaining attached at the one end for a considerable 

 time; ultimately a vacuole appears in the common terminal proto- 

 plasm and final separation takes place. 



Perrin describes a number of different types of Spirocheta balbi- 



