188 
and in the small size and dense spacing of its 
melanophores (see Figs. 2-4). The uppermost 
element in the pattern is a middorsal band of 
melanophores in the skin. It begins at the third 
somite on the 107 -mm larva but is not visible 
until the 15th somite on the 1 2 4 -mm larva. In 
each the row extends to the tail tip. For most 
of its length, this stripe has an irregularly vary- 
ing width of from one to several cells. When it 
meets the anterior end of the dorsal fin (about 
somites 149-153), the row narrows to a single 
file, which extends along the tops of the basal 
elements within the fin. Thus, the pigment cells 
come to lie progressively deeper inward from 
the surface as the thin edge of new fin tissue 
grows upward above the basals. An internal 
supraspinal row of small, densely spaced melano- 
phores runs along the top of the spinal cord 
from the hindbrain to the tail tip, where the 
row ends just ahead of the hypurals. The cells 
are evenly spaced and of uniform size. Another 
internal row of melanophores, between the kid- 
ney and the top of the gut, extends from about 
the 16th somite to the anus. Anteriorly, it com- 
prises a single line of cells, but at about the 
PACIFIC SCIENCE, Vol. XVIII, April 1964 
50th somite the row begins to double, and thence 
continues more or less regularly doubled for the 
rest of its course. An external midventral row 
of tiny melanophores extends from the anterior 
end of the pericardium to the anus. This row 
shows strong zonation in cell abundance (com- 
pare Figs. 2 and 4). The melanophores form a 
wide, densely crowded patch below the pericar- 
dium, and a single densely spaced row from 
there to about the 27th somite (below the pos- 
terior end of the liver). Beyond the liver, the row 
thins out rapidly and its cells are widely spaced 
and inconspicuous until they again' crowd to- 
gether a short distance anterior to the anus. Al- 
though this ventral row underlies the gut very 
closely, it is in the skin rather than on internal 
surfaces. There are no melanophores along the 
midlateral surfaces of the somites, where many 
other kinds of eel larvae bear a conspicuous 
longitudinal row of black cells. Three rather 
inconspicuous patches of internal pigment ( Fig. 
1 ) lie between the midlateral axis and the lower 
edges of the somites, in approximately the an- 
terior half (about 50 to 56%) of the total 
length. They are situated in the vertical connec- 
Fig. 2. Leptocephalus acuticeps. Morphology and pigmentation of head and anterior end of body of the 
107 -mm larva, through somite 16. Somite 4 includes base of pectoral fin; somite 13 marks origin of liver; 
somite 16 includes origin of a major vertical artery. 
