J. W. Jenkinson 
453 
It might be urged therefore that where the part is growing fast relatively 
to the whole its variability is high, while as its relative growth-rate dimiuishes its 
variability decreases too. Thus, between Stages I and II the index value of the 
caudal fin length passes from 4"33 to 1000, but between Stages II and III from 
10-00 only to 12-68, and between Stages III and IV from 12-68 to 13-93, that is 
there are successively diminishing increases of 5 - 67, 2'68, and 1"25, and all this 
time the variability is also decreasing (219, 1'25 and "85). A similar relation can 
be seen between rate of change of index value and variability in the breadth of 
the caudal fin between Stages III and IV. 
That the growth-rate is not however the only factor concerned is seen from the 
fact that in the fifth stage of these two dimensions (length and breadth of caudal 
fin) and between Stages II and III of the latter, a diminution in index value is 
accompanied by an increase of variability. 
A similar relation between the relative growth-rate — as measured by the 
differences between successive index values — and the variability obtains in other 
cases. Thus, although the index value of head-length increases it does so at 
a decreasing rate, and the variability decreases at the same time, so with the 
eye-diameter, the body-breadth, the position of the pectoral and posterior dorsal 
fins, and, but in the final stage only, the positions of the pelvic and ventral fins 
and of the anus. In others the relation does not hold good. It does however 
appear to be true of the majority that the variability depends more closely on the 
relative than we have seen it to do on the absolute growth-rate. 
Correlations. 
Table V gives the values of such correlation coefficients as have been worked 
out in Stages I, III and V. 
The value of the coefficient varies, but between the same pair of correlates is 
of the same sort of magnitude throughout. 
TABLE V. p. 
Total 
Length 
and 
Breadth 
of Caudal 
Fin 
Total 
Length 
and 
Breadth 
of Body 
Total 
Length and 
Length of 
Anterior 
Dorsal Fin 
Total 
Length and 
Length of 
Ventral 
Fin 
Total 
Length and 
Length of 
Posterior 
Dorsal Fiu 
Total 
Length 
and 
Length of 
Head 
Length of 
Head and 
Diameter 
of Eye 
Length of 
Anterior 
Dorsal 
and of 
Posterior 
Dorsal Fin 
Length of 
Ventral 
and of 
Posterior 
Dorsal Fin 
Position 
of 
Pectoral 
and of 
Pelvic Fin 
I 
III 
V 
•888 ±-01 
•736 ±-02 
•727 ± -03 
■790 ±-02 
•869 ± -01 
•764 ±-02 
•493* ±-04 
•602 ±-03 
■836 fOl 
•584* ±-03 
•607 ±-03 
•495 ± -05 
•452 + -04 
•523 ± -04 
•945 ± -00 
•729 ±-02 
•848 fOl 
•766 +-02 
t ("943+ -01) 
■646 ± -03 
■647 ± -03 
•432 ±'06 
■441* ±'04 
•391 ±-05 
•515 +-05 
•646* ±-03 
•581 ±-04 
■872 ±-01 
•691 ±-02 
•825 ± -02 
* Unreliable for the reason already given. 
t The second and higher value is obtained by the omission of one very aberrant individual. 
