SPIROCHATA BALBIANIL AND SPIROCHATA ANODONTA. of 
difficulty at the outset. The habitat of these parasites is in 
the anterior part of the alimentary canal, especially in the 
crystalline style, and occasionally in that part of the liver 
bordering on the stomach. Now the crystalline style very 
soon dissolves and disappears when the oyster is taken from 
the sea.. Even when kept in an aquarium connected with the 
sea, as at Roscoff, the number of oysters possessing crystal- 
line styles, when dissected, is low. A French Professor of 
Zoology informed me that he once left Roscoff with speci- 
mens of a strain of oysters known to be infected with Spiro- 
cheetes, and, after travelling in the train to the south of 
France, found, on arrival at his destination, that the style 
had dissolved, and that the Spirochetes were in most cases 
dead. There seems no doubt whatever that to find the Spiro- 
cheetes plentiful and active in the crystalline style—which is 
probably their principal natural habitat—one must take the 
oysters from the sea and examine them at once. Perrin also 
comments on this fact. 
Yet, on the other hand, Laveran and Mesnil were able to 
find Spirocheetes in oysters freshly procured in the market of 
Paris. But Paris is favourably situated with regard to the 
supply of oysters. 
In my own case, of the specimens bought in the London 
market, about 50 to 60 per cent. of the infected strain 
actually contained parasites. Of these oysters, comparatively 
few, less than 5 per cent., contained crystalline styles. The 
parasites, however, were chiefly confined to the regions occu- 
pied by the style and surrounding structures, namely, the 
stomach, anterior part of the intestine, and the so-called 
cecum. ‘The latter in the oyster openly communicates above 
with the intestine, but is partially separated off by a ventral 
upgrowth or fold of the wall of the gut, a sort of “ typhlo- 
sole.” No parasites were found actually in the substance of 
the ‘‘ fléche tricuspide” of Poli, which is a cuticular lining of 
the stomach. Few parasites were found in the posterior part 
of the intestine or in the rectum. 
I am inclined to think that parasites swimming about freely 
