SMELTS. 
867 
«■ S 
11 11 11 
11 11 11 
Base of the dorsal fin 
Length of the pectoral fins 
Postabdominal length 
Height of the anal fin 
Least depth of the tail 
Length of the middle caudal rays. 
Length of the inaxillaries 
Breadth „ „ ,, 
No immediate descent of the Salmons from the 
Smelts can thus be assumed. 
On examining the relations between the three 
forms hitherto distinguished in the genus of the Smelts, 
we find that the Atlantic Smelt ( Osmerus eperlanus ) 
distinctly appears in some respects to have adopted its 
own course of development, and that in these respects 
it has remained nearer to the presumable origin of the 
genus. But in most points the development seems to 
have been common to the three forms, and the Pacific 
Smelt ( Osm . clentex) is apparently the nearest repre- 
sentative of the original type in the modern fauna. 
We are besides struck by the analogy in the relations 
of development to those between the three above-men- 
tioned Charr forms, Salmo alpinus , S. stagnalis, and 
S. salvelinus, for we find within the genus of the Smelts 
too a defined natural series of three forms, 
Osmerus clentex — 0. spirinchus — 0. eperlanus , 
as the most general expression of the course of evolu- 
tion. Several deviations, however, meet us, which may 
here too be explained as manifestations of the influence 
of sex on the development, the most Arctic form — 
Osmerus. 
Salmo. 
Changes of growth in 
the true Salmons. 
Umbla 
i of the body ° 
14.8 
15.2 
juv. > sen. 
14.4 
b 
8.0 
12.i 
„ > „ 
— 
11 11 11 
14.5 
16.3 
„ > „ 
14.9 
(1 
22.8 
19.9 
ii < ii 
20.9 
11 11 11 6 
7.7 
12.3 
?? ii 
— 
„ „ „ / 
5.i 
8.8 
ii ^ ii 
— 
„ „ „ 9 
6.4 
7.9 
„ > „ 
6.9 
head reduced * 
62.8 
58.i 
ii "" ii 
59.4 
11 11 * 
11.3 
15.4 
ii ?? 
12.4 
maxillaries i ... 
18.o 
26.7 
” > ” 
21.o 
Osmerus 
sp irinchus k , known 
from Alaska, Siberia, 
the White Sea — being differentiated in most respects 
from the other two forms by the predominant in- 
fluence of the female characters, while Osmerus eper- 
lanus, generally speaking, bears the stamp of the male 
characters. 
In order to find an expression for the general 
alterations of growth within the genus, we have dis- 
tributed our specimens among four classes according 
to age, three of these classes fixed by comparatively 
wide gaps in the decrease or increase of the percen- 
tages during growth, the fourth (the oldest) marked by 
a reversion to the earliest characters, best explained, 
perhaps, as the result of a growth exceeding the most 
natural limits of the forms. In certain parts of Swe- 
den a distinction is made in popular language' between 
nors (the smaller Smelts) and slom (the larger ones), 
and at a length of 200 mm. there intervenes in the 
Scandinavian Smelt one of the said gaps, for example 
in the decrease of the percentage for the relative di- 
mensions of the eyes. At a length of about 150 mm. 
we observe a similar gap, and at a length of about 
° Cf. Smitt, Riksm. Salm., p. 9. 
6 
1. c., 
P- 
12. 
c 
1. c., 
P- 
12. 
d 
]■ c., 
P- 
14, 
e 
1. 0., 
P- 
14. 
f 
1. c., 
P- 
15. 
y 
1. c., 
P- 
16. 
h 
1. c. 
P- 
21. 
i 
1. c. 
P- 
21. 
j 
1. e., 
P- 
23. 
k The name of spirinchus was applied by Lilljeborg (Vet.-Akad. Handl. 1850, p. 304) to the White Sea Smelt, and although Pallas, 
who first coined the name, by no means restricted it to that form, we have refrained from giving the said form a new name, as spirinchus 
in its old signification cannot be employed for the future as a specific name. In our first classification of the Salmonoids in the Koyal 
Museum (Ofvers. Vet.-Akad. Furh. 1882, No. 8, p. 34 and Gt. Intern. Fish. Exhib. Loud. 1883, Swed. Cat., p. 184), we called this species 
Osmerus dvinensis. 
1 See Artedi, Descr. Spec. Pise., p. 47 and Nilsson, Skand. Fna , Fisk., p. 433. 
