CILIARY MECHANISMS OF LAMELLIBRANCHS 643 
particles forward to meet those brought on the margin of the 
outer demibranch. ‘This is all moved downward to the lateral 
groove. Apparently there are no similar lines at the base of the 
outer lamella of the outer demibranch, or that of the inner 
lamella of the inner demibranch. 
Palps. On the outer faces of the palps, cilia streams move 
around the dorsal margins to the inner, or apposed faces. Most 
of the material usually moves on to the palp folds, and is then 
disposed of as in Schizotherus. Whether, as in that form, there 
are ventrally directed streams between the folds, and dorsally 
directed ones on their crests, was not determined. The palps 
are narrow, and respond to touch with so great contortion,that 
they are not easily studied. 
Visceral mass. The ciliation of the visceral mass is much like 
that of Mactra, though movement of particles is more directly 
toward its posterior wall, from which it is thrown off to the 
mantle. Here, also as in Mactra, some part of the collection 
may be sent to the dorsal margin of the palp, and if not of too 
great volume, may ultimately reach the mouth. 
Mantle. In Venus and several related forms, as well as in 
some other groups, a distinct line, or narrow path (m in fig. 4), 
extends over the mantle from a point near the lower edge of the 
anterior adductor to the base of the incurrent siphon (b). There 
is a general ciliation, without definite lines or tracts, covering 
the remainder of the mantle wall, and, as indicated in the figure, 
everything on them is moved to the line. An appearance of 
definite lines or tracts is often seen on a surface possessing a gen- 
eral ciliation, because a mucus mass may be drawn out into a 
long thread. Waste accumulates at the bay b, and on contrac- 
Fig. 3 Schizotherus nuttallii; section across palp folds; fd, folds; x, point 
where folds are parted to expose deep cilia tract; 
Fig. 4 Venus mercenaria; mantle ciliation; b, bay of mantle; es, excurrent 
tube of siphon; 7s, incurrent tube of siphon; m, mantle wall. 
Fig. 5 Chione fluctifraga; ec, epibranchial chamber; f, foot; g, gill; p, palp; 
vms, visceral mass. 
Fig. 6 Chione fluctifraga; mantle ciliation; letters as in figure 4. 
Fig. 7 Mactra solidissima; f, foot; p, palp; sm, siphon membrane, vms, 
visceral mass; we, waste canal. 
JOURNAL OF MORPHOLOGY, VOL. 26, NO. 4 
