398 
Spirochaetes of Tapes aureus 
Group D includes Spirocliaetes which appeared rather longer than 
those in group C, with well-marked, expanded membrane showing 
myonemes, and often possessing slightly tapering ends (Text-fig. 2 D, 
PI. VI, Figs. 29—32). These parasites are from 45/a to 70 p long and 
about 1’5/x broad. The waves, into which the body was thrown, were 
not quite of such great amplitude as those of the Spirochaetes of 
group C, so that Spirochaetes of group D are really of about the same 
length as those of group C, and not longer as appeared at first sight. 
The Spirochaetes of group D, stained with Delafield’s haematoxylin, 
are very like S. balbianii of the oyster, except for the slight tapering 
of the ends. Even this character of slightly tapering ends is seen in 
some of the drawings of S. balbianii of the oyster made by Certes in 
1882, and by Borrel and Cernovodeanu in 1907. 
On examining style-preparations from other specimens of Tapes 
aureus, different forms of Spirochaetes may be encountered, thus: 
Tapes 3 contained intermediate forms, especially like those in group B 
(PI. VI, Figs. 14, 22, 23), but possessing more rounded ends than those 
seen in Tapes 1. The stain used was Delafield’s haematoxylin. 
Tapes 4 contained Spirochaetes intermediate in thickness between 
A and B (PI. YI, Figs. 6, 7). Other Spirochaetes on this preparation 
were long and slightly thicker than those of group B (Figs. 24, 27), 
with rounded ends, and bodies clearly showing transverse bars of 
chromatin internally. These Spirochaetes exactly resembled S. balbianii 
from the oyster. They were stained with Twort’s stain. 
Tapes 5 contained many long Spirochaetes with pointed ends 
belonging to group B. Two preparations were made from this mollusc. 
The first preparation was fixed wet with corrosive sublimate and stained 
with gold chloride. The second preparation was fixed wet with osmic 
vapour and stained with Giemsa’s stain. The parasites in each were 
similar. 
Tapes 6 contained a number of short, broad forms, with rounded 
ends (PL VI, Fig. 34), as seen in S. balbianii of the oyster. The 
parasites stained well with thionin. 
Careful examination of a preparation from any one of these 
molluscs revealed the presence of a few Spirochaetes intermediate 
between those grouped under A, B, C and D. To summarise: 
On seven preparations all made by the wet method, from six different 
specimens of Tapes aureus, Spirochaetes of all lengths from 30^. to 
100/r long, and all breadths from 0 - 3p, to 2 - 5ya could be found. Some 
had quite pointed ends, some possessed tapering ends, others were 
