42 ANDERSSON, COMPARISON OF COTTUS POECILOPUS WITH COTTUS GOBIO. 
C. poecilopus. ||  C. gobio. 
| F| 45,2 be ke OR 275,5 
" "19 |43,4| 62,7| 76,1] £2,4| 58 | 758 
Length of the anterior part of the head in 75.51 76.2! 75.4|| 85.2! 91 
4 of the distance between the dorsal fins bd ; ; ika EO 
Q | 70,0] 74,21 70,3] 91,51 89,1] 88,6 
Length of the body in millimetres . . 
The 10 lowest measurements of C. gobio are 73,3—74,1—76,9—78—78,6— 
80—980,5—80,7—81,6—81,7 etc. 
The 10 highest measurements of C. poecilopus are 86,7—83,3—82,6—81,5— 
80—80—79,2—78,9—78,9—78,3 etc. 
As shown just above, there are also in these respects 
many specimens which may be assigned to either of the forms. 
The above examples taken from the measurements in which 
the different course of development, spoken of above, is most 
striking, may suffice to show the great variation in the two 
forms and how they merge into each other. 
Of the specific characters given, which are proved always 
to be useful as distinguishing marks between the forms, only 
the different length of the innermost ventral ray and the 
different distance of the lateral line, measured from the ridge 
of the back, remain. But in the latter of these two charac- 
ters we also find that the two forms are sometimes very 
much alike; and, as regards the innermost ray, this may 
even happen to be entirely wanting. TIf so, there remains no 
character which will hold good as distinctive of the forms. 
My opinion is that in the two, although on the whole they 
show distinct differences in many respects, these differences 
are not as yet so fixed that they can be employed as specific 
characters, for which reason I consider it best not to pro- 
nounce C. gobio and C. poecilopus to be two distinct species, 
but only to range C. poecilopus HEcKEL as a subspecies under 
C. gobio LINNZAUS. 
The specific characters of the different forms would then 
be: Cottus gobio L. forma typica: The innermost ray in the, 
ventral fin is larger than half the length of the fin (about ?/s 
of it); the distance between the lateral line and the second 
dorsal fin is more than 60 2 of the distance from the lateral 
line to the first ray of the anal fin (both the measurements 
