302 
PACIFIC SCIENCE, VoL IX, July, 1955 
TABLE 2 
Actual Mean Ray Counts and Expected Range in Mean Ray Counts for htibknnius edentulus 
and Relatives from Outlying Islands 
ISLAND 
DORSAL FIN 
ANAL FIN 
Actual 
count 
Expected 
range 
Actual 
count 
Expected 
range 
Western Hawaii. 
21.7 
20.3-21.9 
22.2 
22.2-23.2 
Eastern Hawaii 
21.9 
20.3-21.5 
22.3 
22.1-23.0 
Philippines 
20.1 
19.6-20.3 
21.8 
21.6-22.0, 
Line Islands 
20.0 
20.1-20.7 
21.5 
22.0-22.3 
Solomons 
19.9 
19.3-20.2 
21.7 
21.4-22.0 
East Indies. 
20.2 
19.3-20.2 
22.0 
21.4-22.0 
Hawaii and the East Indies are borderline 
instances of the same phenomenon, with the 
Line Islands possibly being so. 
Several questions may be asked in con- 
nection with the above statements, probably 
the most important having to do with the 
validity of the supposed relationship between 
mean annual water temperature and the short 
period in ontogeny in which the number of 
fin rays is determined. Clearly this presump- 
tion can lead to certain errors, particularly in 
the case of fishes living in tidepools, the 
temperature of which is notoriously variable. 
Until further information is forthcoming on 
the embryology of Central Pacific fishes, how- 
ever, mean temperature data must be used in 
working with museum specimens. Annual 
data are perhaps best since they average 
seasonal vicissitudes. 
A second question which arises has to do 
with the taxonomic categories to be employed 
when dealing with a form showing meristic 
differences between various island groups. 
Obviously, if populations from areas repre- 
senting extreme temperatures are considered 
they could be regarded as subspecifically dis- 
tinct. When data are obtained from a more 
or less continuous series of islands, such as 
the band running from the Marianas to the 
Gambiers, however, it becomes apparent that 
extreme populations may be united by an 
evenly graded series. It is possible that spec- 
imens from an island in such a band are 
essentially ecotypes (as used by Dice, 1952: 
397), but because of our lack of knowledge 
regarding the inheritance and adaptive signifi- 
cance of fin ray number this must be left as 
theory at present. It seems more credible that 
populations from a given locale actually rep- 
resent ecophenes, that is, the precise number 
of their fin rays is affected by some environ- 
mental factor such as temperature. In their 
discussion of the response of ecophenes to 
their environment neither Dice (1952: 399) 
nor Alice et ah (1949: 626) mentions the 
heritability or adaptational value of the change 
wrought by the response, and in light of 
Timing's experimental work (1944, 1952) it 
may probably be assumed that neither factor 
is involved in the case of L edentulus. If popu- 
lations within the major distribution of eden- 
tulus actually represent ecophenes then it 
would be superfluous to label them with any 
taxonomic category below the species. 
A third question has to do with the possible 
presence of mutations affecting the number 
of fin rays. It may be argued that the clinal 
distribution of ray counts seen in Table 1 
could be produced by the gradual spread of 
such mutations. If this were so then a muta- 
tion acting to decrease the number of fin rays 
would have to occur near the Equator in order 
to account for the symmetrical distribution 
of ray counts on either side of that region. 
Furthermore, it would also have to occur in 
the Philippines and the Solomons to account 
