250 
The vertical dark bars which are so charac- 
teristic of the manini are absent from the ma- 
jority of night-light specimens. They are faintly 
visible on a few such specimens, however. Ma- 
nini caught in tide pools during the same night 
when they came in usually possess traces of the 
dark bars, but some, presumably very recent 
arrivals, totally lack these markings. One of the 
two previously mentioned specimens which were 
observed just entering shallow water from 
deeper areas of the Ala Wai Yacht Basin had 
traces of the bars, and the other lacked them. 
The bars are not dark on any of the specimens 
collected at night. During daylight of the first 
day of transformation the bars become intensely 
dark brown. This suggests that sunlight might 
accelerate or perhaps even be necessary for the 
darkening. In a review on the biochemistry of 
the production of melanin, Lerner and Fitz- 
patrick (1950: 119) pointed out that ultra- 
violet irradiation appears to be concerned with 
melanin formation in at least four different 
ways, all of which tend to increase pigmentation. 
An experiment was designed to determine 
whether any changes occurred in the transforma- 
tion process when light is excluded. Two trans- 
parent specimens which displayed no evidence 
of dark vertical bars on the body were taken 
at midnight. These were placed in a battery jar 
containing IVz gal. of aerated fresh sea water. 
The jar was covered with a box which, in turn, 
was covered with a heavy black cloth. Three 
other transparent specimens taken at the same 
time were placed in a aquarium of about the 
same capacity which was not darkened. The 
battery jar was uncovered 12 hr. later. The 
transformation of the two specimens had barely 
started. The stage which was reached was about 
comparable to transforming fish taken shortly 
after dawn. The bars on the side were barely 
discernible and the ctenii of the developing 
scales on the posterior half of the body were just 
visible. One of the fish was on its side, dying. 
It was removed, and the jar was again darkened. 
Eight hours later the second specimen was found 
nearly dead. The bars were possibly a little 
darker; the transparency of the body was largely 
replaced by opaque white, an abnormal color 
alteration. The three aquarium specimens com- 
pleted their transformation. The results suggest 
PACIFIC SCIENCE, Vol. XV, April 1961 
that light is essential to normal transformation. 
To be conclusive, however, the experiment 
should be repeated several times. If light were 
conclusively demonstrated to be essential to the 
metamorphosis of the manini, the mechanism 
by which it exerts its effect would still not be 
known. It might act directly on the tissues, or 
by way of the visual sense, or both. 
During the first day the transparency of the 
body is gradually lost. By the end of the day 
the dark brown bars on one side of the body 
cannot be seen through the body from the other 
side as they may be on specimens such as the 
one in Figure 14. The bright silver color on the 
abdomen and head is slightly dulled by the end 
of the day due to the development of melano- 
phores external to the silver layer. The iridocytes 
causing the silver sheen on the abdomen are 
present in the peritoneum. On the gill cover 
they occur in a layer on the underside of the 
opercular bones. They are found on the surface 
of the cleithrum at the edge of the gill opening. 
No silver color is present dorsal to the eye. In- 
stead there is a broad black band which covers 
the brain. This is found beneath the dorsal bones 
of the head. By the third day both the silver 
color and the black band on the head are nearly 
imperceptible. They are, like the rest of the 
body except the region of the dark bars, white 
with numerous, close-set, small flecks of, dark 
brown. The olivaceous cast of the body as seen 
on juvenile and adult manini is not conspicuous 
until about the fourth or fifth day of transforma- 
tion, probably because of slow development of 
yellow chromatophores. 
The second dorsal and second anal spines of 
the acronurus stage are longer and stouter than 
the other spines of these fins (Fig. 14). If stuck 
by either of these spines or by the pelvic spines, 
a stinging sensation almost comparable in in- 
tensity to a bee sting is felt. It is believed that 
these same spines, very elongate in the 6.6 mm. 
manini, are venomous in earlier stages. The poi- 
sonous nature of the spines appears to be a lar- 
val adaptation, for it is lost by the third day of 
transformation. A diminution in the relative 
length of the second dorsal and second anal 
spines may be seen in the series of transforming 
specimens of Figure 17. The relative change in 
length of these spines continues until, in late 
