SPIROCHATA BALBLANII AND SPIROCHATA ANODONTA. 5) 
the morphology of the mussel (27), wherein he mentions the 
occurrence of “spirilliform bacteria” in the gut of Anodon. 
HISTORICAL. 
Spirocheéta ([rypanosoma) balbianii was first re- 
corded by Certes (1) from French oysters in 1882, though 
Mobius (7), writing in 1883, states that he observed the 
parasites in 1869 in the oysters of Schleswig-Holstein. 
Certes gave very good figures of the organism, considering 
the date and instruments of research then available for the 
study of such minute forms. He placed it, more especially 
on account of its possession of an undulating membrane, in 
the genus Trypanosoma, at that time ill-defined and little 
understood. Lustrac (6) in 1896 described longitudinal 
division and the role of the membrane therein. In 1901 the 
famous French protistologists, Laveran and Mesnil (5), 
briefly described the main features of the organism, and 
stated that it was really a Bacterium allied to the Spiro- 
chetes and Spirilla. This paper was, and, in my opinion, 
still is, the most important contribution to the structure and 
affinities of the organism. Spirocheta balbianii has no 
flagellum; yet, in spite of this, Perrin, in 1905-6 (8, 9), still 
retained the parasite in the Trypanosomide, which seems to 
me most distinctly to be a retrograde proceeding. Perrin, 
however, made many excellent observations on the Spiro- 
chetes obtained from Adriatic oysters, but seems to have 
allowed his judgment to have been influenced, at any 
rate to some extent, by a preconceived idea of the 
“ Urhaemoflagellat.” A few other short notes by Vlés (11), 
Swellengrebel (10), and Fantham (8) have appeared recently, 
but no detailed accounts of the movements of the animal, the 
structure of the membrane, or a broad discussion of the 
systematic position of the organism have yet been published. 
Disputed points are whether the membrane is really such or 
only a sheath (“ gaine”” Laveran et Mesnil), whether encyst- 
ment takes place or not (Perrin), and whether so-called 
