456 
BULLETIN OF THE BUREAU OF FISHERIES 
of the body and is contained about 3 times in the standard length, whereas in 10-mil- 
limeter specimens the greatest depth of the head is contained about 2.5 times in 
the standard length. Preopercular spines, long and prominent in the very young, 
are not evident in 15-millimeter fish. The fins are well developed. The ventral 
fins, which first became evident in specimens 7 millimeters long, are long and promi- 
nent in 15-millimeter specimens, reaching to the origin of the anal. The first two 
spines of the anal are well separated from the rest of the fin, as in the adult, and 
the caudal fin is rather deeply forked. Preserved specimens of this size, when viewed 
with the unaided eye, have a brownish cast, especially along the back, a dark blotch 
over the head, and a dark lateral stripe. Under magnification the individual c.hro- 
matophores, causing the coloration, are still visible. In life, specimens of this size 
are quite silvery. 
Specimens 20 millimeters long.—Thz differences between fish of this size and 
those 15 millimeters long is not pronounced. The body, although still notably com- 
pressed, has become more elongated. Scales are not yet present but bony scutes 
in the posterior part of the lateral line are quite evident. The pores of the lateral 
line also are plainly visible. (Fig. 71.) 
Specimens 30 millimeters long . — The body is notably elongate but remains 
quite strongly compressed, the greatest depth being contained about 3.6 times in 
the standard length. The snout has become rather pointed, and the mouth oblique 
and terminal. The tip of the lower jaw is about on the same level as the middle 
of the eye, and the maxillary reaches to or slightly past the anterior margin of the 
eye. The mouth therefore has approached very nearly the shape and position 
occupied in the adult. The bony scutes in the lateral line are developed throughout 
its length. The scales, being very small, are not definitely visible. The ventral 
fins are proportionately shorter than in somewhat smaller fish and reach only to 
the vent. The last two rays of both the dorsal and anal, which are destined to form 
separate finlets, are united by membrane and entirely undifferentiated from the 
rest of the fin until a length of about 30 millimeters is attained. At that size a 
somewhat larger interspace is present between the second and third posterior rays 
of each fin than between the other rays, but generally a membrane still connects 
the last pair of rays with the rest of the fin and the finlets are not fully differentiated. 
The fish now is mostly silvery, the back being slightly brownish in preserved 
specimens, and the dark lateral stripe, characteristic of smaller fish, has disappeared. 
