ox A NEW RHABDOCCELE CO:m:\IEXSAL WITH 
:\IODIOLUS PLICATULUS 
EDWIN LINTON 
Professor of Biology, Washington and Jefferson College 
FORTY-OXE FIGURES 
During the summer of 1909, while searching for sporocysts 
and rediae in the mollusks of the Woods Hole region, at the Bureau 
of Fisheries Laboratory-, I found an interesting turbellarian in 
the ribbed mussel which is not onl}' new to this continent but 
which possesses some characteristics which seem to mark it as 
unique among the Rhabdocoelida. 
The first specimen encountered was taken to be a redia, but 
later when it was noted that not only was the worm ciliated, but 
that it contained cihated young, it was seen to be a viviparous 
rhabdoccele. After much experimenting it was found that the 
worms could be collected to the best advantage b}' opening the 
shells of the mussels and shaking the animals about in a dish of 
sea water The}- are thus washed off the gills and will be found 
creeping about on the bottom of the dish. ]Much time was spent 
in looking over the gills and mantles of mussels in the hope of 
finding some of the worms in place; none were found, however, on 
any part of the animal. This is not to be wondered at when the 
small size of the worms is considered, and further, that the}' are 
practically the same color as the gills. Indeed it happened more 
than once that what was thought to be one of the worms proved 
to be a small piece of gill or mantle which had been torn off by 
accident and was moving about in the water b}^ its own ciliary 
action. 
The species belongs to the genus Graffilla or to a closely related 
genus, but is quite different from any species noted by von Graff 
in his Monographic der Turbellarien. 
