1870.] IN THE GROWTH OF SALMON. 45 
ment being in the less depth of the operculum, and smaller size of 
the dorsal and anal fins. 
The Sewin, excepting in a smaller ventral fin, is almost inter- 
mediate between the three foregoing. The hybrid (?) varies in 
proportional dimensions little from the preceding; the head may 
be considered a trifle longer than in them, as also the distance 
betwixt the dorsal and caudal fins, betwixt the pectoral and ventral 
fins, and betwixt the ventral and anal. Considering that the speci- 
men of S. nigripinnis is a shade larger fish, its admeasurements 
wonderfully harmonize with the five already mentioned. 
What, therefore, appears to be elicited is that, pari passu, the 
fishes No. 1 and No. 2, fully four and five years old respectively, 
are almost identical in the relative proportions of their bodies with 
what may be assumed much younger Parr, Sewin Smolt, hybrid 
Sewin, and the so-called S. nigripinnis. 
Taking column VII. into consideration, and contrasting it with 
III., the relative growths of the several parts of the Salmon’s body 
to each other (from the Parr to the adult condition) are proved to be 
unequal in ratio. The total lengthening of the body, in the instances 
cited, is =7 times. The depth of the body increases x8. The 
head elongates X7°6. The least depth of the tail has an increment 
= x59. The distance from the end of the snout to the eye enlarges 
x 121 times, or in the male the anterior segment of the face is 
proportionally excessively developed, a fact not at variance with the 
proportion between adult male and female Salmon. The maxillary 
bone grows in length x 8°7._ The distance between the eye and the 
opercular angle increases nine times from the Parr to the adult stage 
asa Salmon. The operculum widens x 5-7, and its depth becomes 
=x/7. Betwixt the occiput and the dorsal fin the intervening 
space lengthens by x8*7, and that betwixt the dorsal and caudal 
fin 7°2 times. The elongation basally of the dorsal fin is = x 6:2, 
and its height = x51. The pectoral fin lengthens x 4-4; but 
the increase of distance between the roots of the pectoral and ventral 
fins is = X7*7. The elongation of the ventral fin proceeds to x 5°3 
times, whereas the distance between the root of the ventral and the 
origin of the anal fin becomes = x 10°5. The anal fin grows 5:9 
times as long, the longest caudal ray x 5:6. 
The above data are of course only approximate, as from the 
comparison of only two specimens it would be unfair to draw con- 
clusive deductions ; but, taken for what they are worth, computation 
gives the following general results :— 
1. The average measurements of the development of the body, 
head, occiput to dorsal fin, dorsal to caudal, and pectoral to ventral 
fins are as 7°44 to 1. 
The amount of divergence between the ventral and anal fins, 
10-5 to 1, is much greater than the foregoing maximum and mini- 
mum, an anomaly possibly dependent on sex. 
2. The ratio of increase of the maxillary and the eye to that of the 
operculum averages 8°85 to 1. 
3. The average elongation of the fins is as 5°26 to 1. 
