SPIROCHATA BALBIANIIT AND SPIROCHAITA ANODONTA. 59 
principal agent in progression. Its myonemes set up trans- 
verse movements in the surface of the body, manifested as 
waves passing down the body in a direction opposite to that 
in which the organism moves. 
8. In life, during active movements the membrane is closely 
contracted round the body, and is not easily seen except as a 
halo round the organism. It is more difficult to discern in 
S. anodonte. 
9. The so-called ciliate (flagellate) stages of S. balbianil, 
mentioned by Vlés (11), are really due to the rupture of the 
membrane, and the apparent flagella are really myoneme 
fibrils. No flagellate stage occurs in life. This is probably 
of far-reaching significance, and may explain the discrepancy 
in the accounts given of 8. gallinarum by Borrel and 
Prowazek. 
10. The nucleus is diffuse, and consists of a helix of 
achromatic substance in which small bars or rodlets of 
chromatin are disposed during the trophic condition. The 
helix apparently is slightly looser in periods of activity such as 
division; the achromatic substance is then more evident, 
probably containing scattered chromidia, while chromatin 
masses are seen along the turns of the spiral. 
11. Longitudinal division is common. ‘Transverse division 
also occurs, but far less frequently. This is to be expected 
in long thread-like organisms wherein the longitudinal stress 
is probably less than the transverse, the envelope being 
longitudinally striated. 
12. A small mass of chromatin occurs at either end of the 
periplast of the organism. It may be termed a basal granule, 
and is one of the first structures to show signs of fission in 
forms about to divide. 
13. Regarding the life-cycle, only asexual methods: of 
multiplication, principally by longitudinal fission, are known 
with certainty. 
14. It is interesting to note that Spirocheta balbianti 
was found actively swimming about in sea water in which 
infected oysters had been kept for some time. 
