326 ANDERSSON, COMPARISON OF COTTUS POECILOPUS WITH COTTUS GOBIO. 
The distance of the anal fin from the tip of the snout. 
| C. poecilopus. C. gobio. 
| | 
| 
TUREN 
JA 45,2] 57.5] 76,1) 42,5) 57,91 75,5 
"19 | 43,4] 62,7] 76,1] 42,4/ 58 |75,;8 
Distance of the anal fin from the tip of the [3] 43,1 43,3] 45,7|| 45,1| 46,8) 47,3 
t in 4 of the length of the body. . 
snont in « iof the length of the body. + 10 |434 445) 45.0 SEN 
Length of the body in millimetres . . . 
This measurement increases regularly in both forms and 
is greater in OC. gobio, which in this respect evidently re- 
presents the adult stage. There appears a distinct difference 
in sex in C. gobio, the female having this measurement con- 
siderably greater than the male, but in C. poecilopus this 
sexual difference is wanting, as in the measurement spoken 
of on p. 39. 
Length of the finless part of the tail behind the dorsal and 
anal fin. 
C. poecilopus. | C. gobio. 
[ 345,21 57,5) 76,11 42,51 57,9) 75,5 
19 | 43,4] 62,7) 76,1) 42,4| 58 175,8 
Finless part of the tail behind the 2nd dor- (>) 6,01 5,7) 551) 3 TIN 
sal fin in 4 of the length of the body 19 5.0) 5 | 5,71 Lz) 2 26 
Finless part of the tail behind the anal fin [3 9,6) 9-| 8,5 9,6) 9,8) 9 
in & of the length of the body SRA Se d | 
121 88) 8,8) 8,71 9,7) 9,6) 9,8 
| Length of the body in millimetres . . . .s 
The above table shows the changes in length in the fin- 
less parts of the tail. The figure of this measurement is de- 
pendent on the length of the fins and still more on that of 
the appendant membrane behind these. Thus we find the fin- 
less part of the tail behind the posterior dorsal very much 
shorter in C. gobio and shorter in the males than in the fe- 
males, this being due to the large growth of this membrane 
in C. gobio, especially in the males. "To judge by the table 
we ought to find in this measurement a materially specific 
