452 
BULLETIN OP THE BUREAU OP FISHERIES. 
tion was given to the esophagus in this instance. Carmine was then put into the 
culture and a mass of particles pushed against the gaping valves of the mussel. 
A long stream of red particles shot in through the lower part of the region of the 
inhalent siphon, swept across the gill and between the upper part of the palps like 
a flash, and up the esophagus — a bright red stream — into the stomach. The instant 
the advance end of the stream entered the stomach the valves closed sharply, hut 
the carmine between the palps and in the esophagus passed on into the stomach. 
The valves remained closed and no more material of any sort entered. In about 
10 minutes the loop of the intestine was red in color, showing that the carmine had 
passed through the stomach. 
MUSSELS 3 MM. LONG. 
At this size, while there has been as yet no significant structural development, 
the mussels have by no means remained stationary. Tentacles have developed 
about the siphons, but when the mussel was lying on its side in a watch glass these 
were not extended and visible. A specimen of Lampsilis luteola was placed in a 
suspension of carmine grains. At first a few were ingested, appearing very bright 
and distinct as they passed between the palps. Then the mussel closed and 
remained so. After 10 minutes the experiment was terminated. 
A specimen of Lampsilis luteola with the intestine practically empty was 
placed in a watch glass and some mud from the Mississippi River added to the 
water. This “mud,” upon examination under the microscope, proved to be com- 
posed of sand grains measuring from 3 micra to 20 micra across and of organic 
debris. Some of the latter was as fine as the sand grains; some larger. Streams 
of this material entered the mantle chamber of the mussel in front and on the 
ventral side and passed between the palps, as heretofore described. Heavy streams 
of the material could be seen to pass down the inner face of the outer palp (looking 
through the palp, of course) and along the lower edge to the lower posterior corner 
and off. This end of the palp, especially at the lower corner, would curl upward 
somewhat (Cobb, 1918). A fairly heavy stream or rope of material would be 
streaming down off this comer all the time if any amount of material were entering 
between the palps. The streams of material passing down the inner face of the 
palp were in fixed vertical rows, without doubt corresponding to the positions of 
the transverse ciliated grooves on the inner face of the palp. At times particles 
passed along across the inner face of the palp and forward to the mouth and could 
be watched until they entered the stomach. These particles usually passed across 
the upper part of the palp, in the apex of the inverted V formed by the apposing 
faces of the palps. Since the upper part of the palp is more opaque than the rest, 
only the larger particles could be followed to the mouth, and it is almost impossible 
to observe fine particles passing along the esophagus unless they are brightly col- 
ored. It would seem, however, that many smaller particles must have passed 
forward and been ingested, since the intestine was filled and feces were being dis- 
charged in less than an horn after the beginning of the experiment. The mussel 
was fixed and sectioned and a photomicrograph of a portion of the intestine is shown 
