480 
BULLETIN OF THE BUREAU OF FISHERIES 
the left side of the head, as in the adult; the abdomen no longer protrudes; the body 
has definitely acquired the shape of the adult and is completely scaled ; the anterior 
rays of the dorsal fin are no longer filamentous; the rudimentary pectoral fin has 
disappeared almost completely; a ventral fin in advance of the anal is evident for 
the first time; the mouth is horizontal and slightly inferior; the premaxillaries have 
acquired a pronounced curve ns in the adult; and pigmentation has become general, 
distinctive color markings consisting of dark bars. Our material suggests a sudden 
metamorphosis soon after a length of 10 millimeters is reached or perhaps that no 
Figure 95 . — Symphurus plagiusa. From a specimen 10 millimeters long 
increase in the length takes place during this critical stage. For example, a specimen 
fully 10 millimeters long still has the eyes on the opposite sides of the head, the right 
one being situated only a little higher and slightly in advance of the left one; the 
abdomen protrudes, much as in smaller larvce; and the anterior rays of the dorsal 
are still filamentous. An 11-millimeter specimen, on the other hand, has virtually 
all the characters of the 13-millimeter specimens described in the foregoing lines. It 
is quite probable, of course, that some variation in the length at which adult char- 
acters are acquired occurs among individuals. It is expected, that in some indi- 
viduals the eyes, for example, will become situated on one side of the head at a some- 
what smaller size than in others. Insufficient material is at hand, however, to show 
the exact variations, for we have comparatively few specimens ranging from 7 to 
15 millimeters in length. These specimens also fail to show the complete migration 
of the right eye to the left side of the head, notwithstanding that one or a few speci- 
mens are at hand for each 1 -millimeter group, ranging in length from 8 to 15 milli- 
meters (the range in size during which the metamorphosis takes place). In 10- 
millimeter specimens, as already explained, the migration of the eye appears to have 
