SPORE-FORMATION IN THE DISPORIC BACTERIA. 581 
in pure culture, as my object has been to study their ordinary 
ways of life, and not those occurring under artificial con- 
ditions. 
THe Meruop or Spore-FORMATION IN BACILLUS 
SPIROGYRA. 
I have already (1908) given a brief description of the 
organism which I have named Bacillus spirogyra. I will 
here briefly recapitulate its main characteristics, and make a 
few additions and corrections to my original description. 
B.spirogyra is a bacillus of large size—attaining a length 
of 12 by ca. 2 u—which I have found in the large intestine 
of frogs and toads, chiefly the latter. It is very uncommon. 
The most striking characteristic of this Bacillus is a spiral 
filament which runs from end to end. This filament varies a 
good deal in the way it is disposed. Sometimes it appears 
almost straight (Pl. 15, fig. 1), though as a rule it is in the 
form of an irregular spiral or zig-zag (fig. 2). Occasionally 
the filament is very much contorted (fig. 3). It is always 
deeply stained by nuclear stains—especially good differentia- 
tion being obtained with Giemsa’s stain and Heidenhain’s 
iron-hematoxylin. From its constancy and staining proper- 
ties 1 think it is justifiable to regard this structure as a 
nucleus. Owing to the refractivity of the organism’s pellicle, 
the filament cannot be made out with certainty in the living 
cell. I have never found any granular or other inclusions 
in the cells. 
Spiral filaments such as this have already been described 
in several Bacteria—notably by Swellengrebel in Bacillus 
maximus buccalis (1906) andin Spirillum giganteum 
(1907). They have also been figured frequently in spiro- 
chets. Several recent investigators have considered that 
these filaments do not really exist as independent structures ; 
they suppose. them to be merely an appearance due to the 
arrangement of the granules and protoplasmic alveoli of the 
