BIHANG TILL K. SV. VET.-AKAD: HANDL. BAND 24. AFD. IV. N:03, 39 
ventral fins. The more developed lateral line, and the fact 
that it runs nearly along the middle of the body, may well 
be representative of a more primitive character than the state 
of things in OC. poecilopus is, in which the lateral line, pro- 
bably by the decrease of it in the primitive form, is very 
slightly developed, approaching at the same time very near the 
back. A uniform development appears in the jaws, the paired 
fins, the caudal fin, the depth of the head, and that of the 
anterior part of the body. An opposite development we find 
in the innermost ray of the ventral fin, partly also in the 
distance of the lateral line from the back, in the length of 
the belly, and in the length of the anal fin in proportion to 
its distance from the tip of the snout. 
As the one form may be said to represent a more juve- 
nile stage and the other a more adult one, we may also say 
that the one represents a male stage, the other a female. 
C. gobio usually represents the male stage on the ground 
that the male is usually more developed than the female, but 
sometimes in certain respects C. poecilopus represents the 
male stage, as for example in the length of the unpaired fins, 
as also in the development of the belly. 
The fresh-water Cotti have probably at an early period 
begun to differ from their salt-water relations, from whom 
they at present differ very widely. Some of the characters 
which mark the genus Cottus seem to have been afflicted by 
their living in fresh water, which hindered their development 
and sometimes caused even a decrease, this being especially 
noticeable in that branch which more than the other has be- 
come a fresh-water form and an inland one, viz. C. poecilopus. 
A comparison between the fresh-water forms and the 
brackish-water ones of C. gobio strengthens such a supposition. 
| 
Fresh-water | Brackish-water 
specimens. specimens. 
| 
| 110 sp.|20 sp.|' All [15 sp.|10 sp.| All 
| Gör 20 Ispeell oe QEspec! 
| 
I 
| | | 
Length of the body in millimetres . . | 50,8 | 61,3 | 57,8) 64,5 | 61,11 63,1 | 
. I I 
Length of the head in 4 of the length | | | 
FREE HE RTV SS ST SET oh Sp SE ET 26,0 | 26,2 | 26,1 || 26,5 | 26,8) 26,61 
Length of the cheek in 4 of the length 
Stherbödgrt stole bhus RI 3: 11,22 ND TRLA 
