828 
SCANDINAVIAN FISHES. 
fat for the time when they must resort to fresh water 
for the reproduction of their species. 
The Scandinavian genera of this family are the 
following: 
A: Dentition strong, even the tongue fur- 
nished with teeth. Length of the maxil- 
laries more than 53 % a of that of the head 
reduced (from the Lind extremity of the 
intermaxillary bone to the posterior mar- 
gin of the preoperculum). Base of the 
dorsal fin proper shorter than the head 
reduced. ( Salmonince ) 
1 : Branched rays in the anal fin lessthanlT. 
a: Transverse rows of scales on the 
sides of the body more than 100.. Genus Salmo. 
b: Transverse rows of scales on the 
sides of the body less than 80 Genus Osmerus. 
2 : Branched rays in the anal fin at least 17 . Genus Mallotus. 
B: Dentition weak or teeth wanting, at least 
the tongue toothless 6 . Length of the ma- 
xillaries less than 53 % of that of the 
head reduced. ( Coregonince ) 
1: Base of the dorsal fin proper more 
than 15 % of the length of the body 
and longer than the head reduced Genus Thymallus. 
2: Base of the dorsal fin proper less than 
15 % of the length of the body. 
a: Base of the dorsal fin proper more 
than half the length of the head 
reduced Genus Coregonus. 
b: Base of the dorsal fin less than half 
(<45%) the length ofthe head reduced Genus Argentina. 
In this manner we have endeavoured to find an 
expression for the said two directions of development. 
The development, however, has not been so regular that 
a sharp and fixed line can be drawn between two di- 
stinct subfamilies; and the intermediate position occupied 
by the Graylings (genus Thymallus) may perhaps justify 
the establishment of a third subfamily, characterized 
principally by the advanced development of the dorsal 
fin. The community of origin in the case of all these 
genera affords an explanation of the fact that the fry 
of the most differentiated forms in one group show 
points of resemblance to the other group. 
In order rightly to comprehend the relations be- 
tween the genera, it is indeed necessary to have a 
knowledge of the exotic forms as well. But two of the 
Scandinavian genera are so rich in forms, even within 
the limits of our fauna, that in them we may trace the 
development of form in its past course and, seemingly, 
in its present continuation. 
ovd 
Fig. 208. A gravid female Smelt, taken at Stockholm on the 19th 
of April, 1892. Natural size, ovs, left ovary, with eggs arranged in 
transverse rows; ovd, lower (posterior) part of the right ovary; m, 
margin of the mesoarium, which envelops the ovary both above (in 
front) and below (behind) even on the left (outer) side, but below, 
owing to the coalescence of the margin with the wall of the abdomi- 
nal cavity, forms a funnel-shaped duct, open above at a; r , rectum; 
an, vent; gu , situation of the genital and urethral apertures, the for- 
mer in front of the latter, drawn as a common opening because the 
wall between them could not be distinguished externally. 
a Exceptions occur among Salmon fry. 
„ Grayling „ 
b 
