H. B. Fantiiam 
397 
This specimen Tapes (No. 1) contained many Spirochaetes of group 
A, a fair number of group B, and relatively few of group C. 
The internal structure of chromatin granules or bars could be well 
seen in forms B and C, while in the very thin forms A it was with 
great difficulty, owing to the thinness of the organisms, that any 
internal structure could be demonstrated. 
Text-fig. 2. Diagrams of various Spirochaetes found in the crystalline style of Tapes 
aureus. 
A. Thin form, possessing clearly defined edge to its membrane. 
B. Slightly broader, longer form, with pointed ends. 
C. Broadest form, with contracted membrane, the edge of which is represented as 
a wavy, black line along the body. Ends tapering. 
D. Spirochaete of medium breadth, with slightly tapering ends. 
The groups A, B, C, D are really arbitrary ones, for various intermediate forms occur, 
so that they gradually merge into each other. 
At first sight, it might be inferred from these observations that 
more than one species of Spirochaete was present in the crystalline 
style of the mollusc examined, or that sexual polymorphism was 
exhibited by the Spirochaetes. However, many more specimens of 
infected T. aureus were examined, when other Spirochaetes, chiefly 
intermediate in form, were found. These molluscs may, for convenience, 
be denoted successively as Tapes 2, 3, 4, 5, etc. 
Thus, on examining a preparation from the style of Tapes 2 large 
numbers of another form of Spirochaete were found, which may be 
called group D. 
