448 G. CLIFFORD DOBELL. 



when the colour has been sufficiently extracted from the cell 

 wall to enable one to see the iuternal structures, then the 

 cell contents have also been so much decolorised as to be 

 almost invisible. Now and then, however, clear pictures of 

 the protoplasmic structures can be obtained. 



In well-stained individuals I have invariably found the 

 same structure present. There is no vesicular nucleus visible 

 aiid no nuclear filament. The only structures which can be 

 seen are shown in figs. 110-112 (PI. 18). The cytoplasm is 

 alveolar, the alveoli sometimes extending across the whole 

 width of the cell, sometimes being of smaller size. At various 

 points in the walls of the alveoli lie deeply staining granules. 

 They are usually few in number, very irregularly arranged, 

 but generally in close proximity to the cell wall. Occasionally 

 two or more granules appear at first sight to be connected 

 with one aiiother by fine intervening filaments; but it seems 

 to me that in all cases these filaments are really nothing more 

 than the alveolar walls. I have never found any structure at 

 all comparable with the nuclear filament of B. spirogyra 

 and similar forms. 



My interpretation of the appearances observed in the large 

 Spirillum of the cockroach is therefore this : The structure 

 is essentially the same as that of B. flexilis and allied 

 organisms. The cytoplasm is alveolar and the nucleus is in 

 the form of chroraidia — consisting of a few small, scattered 

 granules of chromatin lying in the walls of the alveoli. 

 Neither vesicular nucleus nor nuclear filament exists in the 

 forms which I have examined. The structure is therefore 

 closely similar to that of S. monospora. 



(b) Spirilla with Nuclei of Filamentar Form. 



There is a large Spirillum^ which lives in the gut of 

 Lacerta m uralis. I have found it much easier to study 

 than the large forms from the frog and the cockroach, and 



* These are the organisms to wliich I referred in a previous p;iper 

 (Dobell, 1909. p. 583).' 



