H. B. Fantitam 
403 
One of the Tapes from the first batch which was uninfected with 
Spirochaetes, so far as could be ascertained without injuring the living 
specimen, was placed in an aquarium of sea-water along with several 
living oysters containing S. balbianii. After a period of three weeks 
the Tapes was dissected and found to be infected with Spirochaetes, 
which were identical morphologically with S. balbianii. In all 
probability, then, the specimen of Tapes had become infected with 
S. balbianii derived from the oysters kept in the same aquarium. I 
have previously recorded (vi. 1907, p. 500; I. 1908, p. 10) the fact that 
S. balbianii was found swimming about freely in a basin of sea-water 
in which infected oysters were being kept alive. I think it is almost 
certain that Spirochaetes from the oyster had swum into the water of 
the aquarium and infected the Tapes per os. Further infection experi¬ 
ments of this nature are necessary. Rigorous proof of the conveyance 
of infection by the water can only be obtained, however, by breeding 
young Tapes from parents definitely known to be uninfected, in sea¬ 
water also known to be free from Spirochaetes, and then placing infected 
oysters with the Tapes. I hope to have an opportunity of investigating 
this problem in the future. 
Oysters and Tapes may occur together naturally. The Spirochaetes 
found in Tapes aureus seem to me to be Spirochaeia balbianii or only 
varieties of the same. It is probable that S. balbianii occurs in many 
marine Lamellibranchs. 
As corollaries to the foregoing observations I would suggest that 
it is not entirely wise to create many new species of Spirochaetes—as 
Schellack (1909) has done—because of their occurrence in different, 
yet often closely allied, marine Lamellibranchs, without first examining 
large numbers of Spirochaetes from each host. Such extended examina¬ 
tion is necessary in order to acquire knowledge of the morphological 
variation of the Spirochaetes. Furthermore, infection experiments 
should also be considered. 
Conclusions. 
(1) The Spirochaetes of Tapes aureus are probably all referable 
to one species, for a continuous series can easily be found embracing 
long and short, narrow and broad forms, also Spirochaetes with sharply 
pointed, tapering or rounded ends and others whose two ends are 
unequally pointed or rounded (PL VI, Figs. 1—37). 
