BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 24. AFD. IV. N:0 8. 97 
distinction between the forms, but, looking more closely into the 
matter, there seem to exist great variations and also many 
intermediate forms. The finless part behind the anal fin, where 
the appendant membrane is very small, is longer in OC. gobio 
and longer in the female than in the male, as a consequence 
of the more advanced growth of the anal fin in the male and 
in C. poecilopus. In the male these measurements diminish 
with age, in the female the measurement of the finless part 
behind the dorsals increases, while that behind the anal al- 
ways remains of the same length, the two forms being alike 
in all these respects. 
The distinction between the two forms seems then to be 
found only in the development of the appendant membrane 
behind the second dorsal. In OC. poecilopus this membrane is 
less developed, showing a juvenile and a female character, 
this membrane being less developed in the younger than in 
the older specimens, and also less in the females than in the 
males. The different courses of development of the males and 
females must also be noticed. In the males this appendant 
membrane increases with age, in the females it diminishes. 
The lateral line. 
I C. poecilopus. ; OC. gobio. 
| 
45,21 57,51 76,1 42,51 57,9) 75,5 
4 2,7| 76 
5,1 42,4/ 58 |75,8| 
i | I 
Length of the body in millimetres . ps I 
i 
Distance between the lat. line and the 2nd | | | 
dorsal fin in & of the distance between the [3] 49,1| 43,2 49,31 71,4] 70,9] 70,2 
lat. line and the first ray of the anal fin. = Alle & - 
19 | 48,8| 47,1| 49,31 75,6| 73,9| 70 
I have already spoken of the difference in distance of 
the lateral line from the ridge of the back. I should like 
now to add a few words on this point. As in the innermost 
ventral ray, so in this respect we find to some extent. a dif- 
ferent course of development. "The lateral line in C. gobio 
seems to approach nearer the back, which at an earlier pe- 
riod was also the case with C. poecilopus, traceable in the 
great diminution of the measurements going from the small 
specimens to the middle-sized. In OC. poecilopus, however, 
