522 
BULLETIN OF THE BUREAU OF FISHERIES 
rayed fishes studied, no spines are visible at this size on the preopercular margin. 
The vent now is situated at midbody length, without caudal. The development of 
the fins has progressed rather rapidly. The spines in the dorsal and anal are well 
differentiated; the caudal fin is long and round, being nearly as long as the head; 
the pectoral fins, too, are long, reaching the vent; but the ventral fins are minute, 
being scarcely longer than the pupil. 
The only change in color, worthy of note, is the development of additional dark 
dots along the ventral outline of the chest and abdomen, which vary in number 
among individuals. Some specimens also have developed a few extra chromato- 
phores on the dorsal surface of the head. 
Specimens IS to 15 mm long . — No measureable changes in the proportions of the 
body have taken place. However, the snout has decreased in proportionate length 
and is definitely shorter than the eye, 3.6 to 4.0 in the head, whereas the eye is con- 
tained 2.8 to 3.0 times in the head. The mouth remains oblique, the gape anteriorly 
being only slightly below the level of the middle of the eye; the maxillary reaches 
only slightly beyond the anterior margin of the eye; and the teeth remain minute. 
The skull remains transparent, leaving the brain plainly visible from above. The 
rays in the dorsal and anal are all developed as the usual number present in adults 
may be counted, but the spines remain proportionately much shorter than in the 
adult. The caudal fin becomes square when the fish attains a length of about 12 mm 
and is definitely concave at a length of about 14 mm. The pectoral fins remain long, 
reaching nearly to origin of the anal; and the ventral fins have increased greatly in size, 
being nearly as long as the eye in 15-mm fish, but the spine is not yet well differentiated. 
No changes in color markings worthy of note have taken place since a length of 
about 10 mm was attained (fig. 14). 
Specimens 18 to SO mm long . — Specimens of this length are variable in shape and 
color. Some specimens up to 20 mm in length remain quite as slender as 15-mm fish, 
whereas others are notably deeper. The slender specimens of this size are as void of 
pigmentation as 15-mm fish, whereas the deeper bodied specimens are profusely 
pigmented and have dark cross bars as in the adult. A few specimens only 16 to 17 mm 
long already have increased considerably in depth and have evident cross bars, 
whereas others up to 20 mm in length remain slender and pale. It is evident, there- 
fore, that pigmentation and the deepening of the body take place simultaneously 
and that these changes occur at varying lengths. These changes apparently are 
associated with a change in habitat, as shown subsequently. 
The depth is contained in the length to the base of the caudal 4.3 to 4.5 times 
in three unpigmenfced specimens measured, whereas in three pigmented fish of the 
