(TryP'inosonia) Balbianii and S. aiiodontic. 497 



gists — to whom I have shown these Spirochsetes alive, have 

 compared their luotioa to that of an eel, or the embryo of 

 Filaria, or to that of Nereis^ but with the spiral movement 

 in addition. 



General Structure. 



Tlie general shape of each of these Spirochsetes is tliat of 

 a long narrow thread. S. Balbianii varies from 50 /ju to 

 l')0 /M in length, and is 2 fi to 3 /jl broad. Its breadth is 

 almost uniform and its ends are rounded. S. anodontce is 

 about 35 /x to 40 yu- long and about 0'7 /u, broad. Keysselitz [4] 

 did not give the dimensions of his parasite from A. mutabilis. 

 The ends of S. anodontce are pointed and prolonged into a 

 filament-like process, which some observers might be disposed 

 to call a flagellum, though it seems to me to be stiff. 



The body is bounded by a well-marked periplast which 

 encloses a homogeneous cytoplasm. There is no marked 

 differentiation of this cytoplasm into ectoplasm and endo- 

 plasm, though I tliink the periplast represents an ectoplasm. 

 The periplast is not composed of cellulose (as tested by iodine 

 and sulpliuric acid), but might be composed of " fungus- 

 ceilulose " so far as negative evidence goes. Perrin, judging 

 from macerated specimens, considered the periplast to be 

 fibrillar in structure. This is very difficult to corroborate, 

 but is probably correct, for these fibrillse might equally belong, 

 in macerated specimens, to the membrane, to be described 

 in the next section. 



In the centre of the thread-like organism is a core of 

 chromatin, the nucleus, stretching nearly from end to end, 

 which consists of a filament on which are arranged transverse 

 bands or rodlets of deeply staining chromatin at more or less 

 regular intervals. These rodlets may be perhaps termed 

 " chromosomes," as by Perrin ; many are irregularly dumbbell- 

 shaped, while some are thinner than others. Perrin considered 

 the connecting spiral or zigzag-shaped filament to be a 

 karyosome. He figures various nuclear changes in connexion 

 with gamete formation, which are, however, open to varied 

 interpretations. In preparation for longitudinal division the 

 dumbbell-shaped rodlets divide, and leave two rows of 

 " chromosomes/' one on each edge, along the periphery of 

 the parasite. I have not seen definite evidence of reducing 

 division. 



The nucleus was not observed by the earlier writers on 

 these parasites. It is of a diffuse character, and there is no 

 definite blepharoplast, facts first noted by Laveran and Mesnil, 

 the significance of which is of the highest importance 



