30 ANDERSSON, COMPARISON OF COTTUS POECILOPUS WITH COTTUS GOBIO. 
This fin becomes shorter (lower) with age in both forms, 
being about equally developed in both sexes and both forms. 
Only in the smallest specimens of C. gobio the caudal fin is 
distinctly longer (higher) than in the corresponding ones of 
C. poecilopus, being a character, which, accompanied also by 
a slightly greater length of the fin in the older specimens of 
C. gobio, recalls to mind the course of development in the 
dorsal fins. C. gobio thus seems as regards all the unpaired 
fins to remain nearer the juvenile stage than OC. poecilopus. 
The middle rays are here always branched, and as in the 
ventral and pectoral fins this branching is more marked in 
the older specimens. "The two forms have almost the same 
number of branched rays. Both forms have as a rule 7 or 8 
such of these. A great many specimens of C. gobio exceed 
this number; as also there are many specimens of C. poeci- 
lopus, which do not even come up to it, thus showing that 
there exists a somewhat greater amount of branching in C. 
gobio. In the ventral and pectoral fins also, C. gobio seems 
to have more rays branched than OC. poecilopus, which latter 
again in this character represents the juvenile stage. I give 
below for the sake of completeness the number of the branched, 
rays in the different specimens. 
Out of 65 specimens (32 >, 33 9) | Out of 50 specimens (29 s, 21 2) 
of C. gobio | of OC. poecilopus 
4 (all small 9) had 2—5 branched rays. 3 (small or middle- 
16 Ers : 3 ; | sized >) had 3—5 branched rays. 
sving, Yrsa satulen tt Rön : 
10(6 7;4 2) ; 9 . 4 MT (BRON F6 > > 
2(5) j 10 | 22 (10 7,122) > S , > 
1 (8) > 9 2 » 
The paired fins. 
— — AE — 
C. poecilopus. || OC. gobio. 
(| 45,2] 57,5| 76,1] 42,5| 57,9 750 
AQ | 43,4] 62,7| 76,1] 42,41 58 | 7548] 
Length (height) of the pectoral fins in 4 of f5 20,9) 21,3] 22,11 21,6] 21,4 21,8! 
the length of the body föl 120,8 ol 21,5) 21,3) 22,3] 2,9 
7 
1 
Length of the body in millimetres . 
Length (height) of the ventral fins in 2 of lan 17,2) 17,7) 20,1) 17,2] 17,71 18,1 
the length of the body 
UGN LOS: 
1757] AT) LO 
