38 H. B. FANTHAM., 
staining zig-zag connections (PI. 1, fig. 3) not very evident 
and so probably not always seen in the first-mentioned forms. 
However, these irregularities can be explained by correlation 
with yet a third set of forms, already mentioned, wherein 
there is a spiral thread in which granules of chromatin are 
distinctly seen (Pl. 1, fig. 5; Pl. 2, fig. 27). These various 
forms of the nucleus are illustrated in text-fig. 9. 
It seems, then, that the nucleus of these Spirochetes really 
consists of a spiral achromatic portion on which granules of 
chromatin are arranged. ‘The question next to be con- 
sidered, is the chromatic filament a spiral flattened into a 
zig-zag in the median longitudinal plane, forming a core to 
the organism, and passing down the centre of the body, or 
is it a marked helix (comparable to the solenoid of the 
physicist), with the coils of the helix coming near the surface 
of the body, that is, almost touching the periplast? The 
latter alternative is, I think, the correct one—namely, that 
the rodlets or granules are arranged on a helix rather more 
loosely coiled at some periods in the life of the parasite than 
at others. 
Analogous conditions of the nucleus have been briefly 
described by Schaudinn (21, 34) in the case of Spirocheta 
plicatilis, where the diffuse nucleus consists of a spiral 
thread on which occur masses of chromatin at regular inter- 
vals. The spiral filament, judging from Schaudinn’s figures 
is not entirely achromatic, but may contain some chromatin 
in the form of chromidia disposed along it. , 
I have myself examined some of the Spirillar forms occur- 
ring in the hind gut of the Cockroach. There are examples, 
apparently, of at least two genera, Spirillum and Vibrio. 
However, I have not gone into the question of the systematic 
position of the Bacteria occurring there, but rather an 
examination of the condition of the nucleus of such forms. 
After fixation of wet films with osmic vapour, also with abso- 
lute alcohol, and staining with gentian-violet, which revealed 
the presence of terminal flagella in the Spirillum, a diffuse 
nucleus was observed (Pl. 2, figs. 24—26), consisting of a 
