596 
BULLETIN OF THE BUREAU OF FISHERIES 
viduals or adults kept long in the aquarium, with which it is always very pale or 
wanting. The color varies from light green almost to black. Indeed frequently the 
visceral mass of juvenile scallops might fairly be termed black. 
Overlying the gonads and surrounding the visceral mass is a tough transparent 
membrane. This may be so removed as to retain the epithelium, spread in sea water 
on a slide, covered with a slip, and examined under high magnification (3 millimeters 
water immersion). It thus appears that the coloring is due to granules of two colors 
Figure 16. — Ciliary currents of mantle and visceral mass; a, right pallial lobe (after Kellogg); b, left side of 
visceral mass with bass of foot shown at left and pigmentation represented by stippling (from observa- 
tions on the movement of fine carborundum); c, ciliary currents of visceral mass of P. tenuicostatus (after 
Kellogg) 
grouped in the epithelial cells. Some granules are yellow, others dark. Under the 
microscope these darker granules sometimes appear decidedly blue but may be green. 
It can be seen that some cells contain only the lighter granules. Others appear to 
contain only the darker ones. Some cells, even in darkly colored areas, are almost 
devoid of colored granules. 
Fixed and preserved material does not retain the greenish color, appearing brown 
instead, but has the advantage that it may be sectioned and a different view of the 
Figure 17. — Pigmented epithelium of the visceral mass (from material fixed in Bouin’s) 
epithelium obtained. In sections cut at right angles to the surface, the disto-proximal 
arrangement of the granules in the epithelial cells may be seen. Although distinct 
color difference has been lost, dark and light pigmentation may still be observed. As 
shown in Figure 17 the granules, particularly the dark granules, lie principally near 
the outer surface of the epithelium. 
Because of the evident and unfailing loss or great reduction of this bodily colora- 
tion with scallops in poor condition, the writer suggests that the pigmentation is 
connected in an important way with feeding or metabolism. 
