58 
PACIFIC SCIENCE, Vol. XVII, January 1963 
Fig. 8. Fin rays in the left pectoral fin presented as 
a function of °N latitude. Materials and place names 
in Table 2. Large rectangle, one standard deviation on 
either side of mean (triangular prominence); black- 
ened space, two standard errors on either side of mean; 
lower horizontal line, range of counts. Open rectangle, 
Pacific Coast populations; vertical lines in rectangle, 
Salton Sea population; oblique lines in rectangle, Gulf 
of California populations. 
Coast (San Francisco Bay and Bahia Santa 
Maria), for instance, is highly significant: F = 
16.9, F 0.975 (29, 29) = 2.1. 
The intrinsic variability in the number of 
elements in a given fin is associated with the 
latitude where the population is situated. In- 
creasing variability is associated with higher 
latitudes (Fig. 10). All the fins manifest this 
increase in variability from south to north, 
though not equally well. If one were to rate 
the correlations subjectively from good to poor, 
they would stand in the order ( 1 ) first and 
second dorsal fins, (2) combined counts, (3) 
anal fin, and (4) pectoral fin. Only the data 
from the first dorsal fin are presented here 
(Fig. 10); the other data are available on re- 
quest. There also may be a positive correlation 
between latitude and variance of the vertebrae 
(see below). 
The correlation between degrees of latitude 
and variance of the first dorsal fin has a coeffi- 
cient of 0.848, which differs significantly from 
a coefficient of zero. This high degree of cor- 
relation doubtless could be increased further 
by reducing that portion of the intra-population 
variation resulting from sampling techniques, 
thereby improving the estimate of the real vari- 
ance. As will be seen further on, comparisons 
of relatively homogeneous year classes from suc- 
ceeding years show that even though the mean 
number of elements in the various fins may 
change, the variance remains the same. Some 
Fig. 9- Combined elements, segmented and unseg- 
mented, in the first and second dorsal, anal, and left 
and right pectoral fins, presented as a function of °N 
latitude. Materials and place names in Table 2. Large 
rectangle, one standard deviation on either side of 
mean (triangular prominence); blackened space, two 
standard errors on either side of mean; lower hori- 
zontal line, range of counts. Open rectangle, Pacific 
Coast populations; vertical lines in rectangle, Salton 
Sea population; oblique lines in rectangle, Gulf of 
California populations. 
