450 
BULLETIN OF THE BUREAU OF FISHERIES. 
was drawn in at the anterior end or ventral side and fell upon the gill (the inner — 
the outer not being developed yet) and was carried forward to the palp. The outer 
palp lifted at the posterior end and caught the Euglena under it. Owing to the 
transparency of the tissues the strong electric light thrown up from below made it 
possible to see the bulky green Euglena carried forward between the apposing 
faces of the palps, move slowly behind the anterior adductor muscle, and up the 
esophagus slowly for about half the way, then with increasing speed until it fairly 
shot into the stomach. After a time a number of Euglenas could be seen being 
whirled about in the stomach by the cilia there. 
Another specimen of Lampsilis luteola was taken from the rearing trough where 
it had been feeding actively, the intestine being full (as observed through the shell), 
and put at once into a culture containing carmine grains, 
Euglenas, and some smaller unidentified orga nism s. The 
mussel opened the valves at once and carmine, Euglenas, 
and the other organisms were all seen to pass up the 
esophagus. In about 30 minutes the intestine was red 
back to the anterior end of the rectum, which still con- 
tained some of the material previously ingested. 
Three specimens of Lampsilis luteola were observed 
while in a suspension of carmine grains. The current of 
particles entered at the anterior end. The particles could 
be seen to be carried quickly back past the anterior part 
of the visceral mass, practically without touching it, and 
to fall upon the gill (the inner) . They passed down the 
gill, as stated by Allen (1914) and Kellogg (1915), to 
the lower edge and forward along this to the anterior end. 
In adult mussels there is a ciliated groove along the lower 
edge of this gill (fig. 3) through which the food is carried 
(Posner, 1875, and Bush, 1922). From the gill the carmine 
particles passed between the apposed faces of the palps. 
A great deal of it was carried downward and passed off the 
the groove bear no cilia and secrete lower posterior corner of the palp. While in this experi- 
Bush)’ aCCOrdmgt ° BUSh (After men t none was actually seen to enter the mouth, the lower 
loop of the intestine (fig. 2, p. 449) soon became quite red, 
showing that carmine had been ingested. After a time the mussel ceased 
ingesting and closed. 
MUSSELS 2 TO 2.5 MM. LONG. 
As far as the structures involved in ingestion are concerned, there is no marked 
advance in a mussel of this size from that of one measuring 1 mm. in length. The 
rudiments of the siphons are beginning, but there are no tentacles apparent, and 
the material enters the mantle chamber at various points from just below the region 
of the inhalent siphon to the anterior end. These points may vary from time to 
time in the same mussel, or the currents may enter at two or three points at once. 
In many mussels up to at least 4 or 5 mm. in length it is not at all uncommon to 
observe particles entering the anterior end and the ventral side simultaneously. 
