FOUR-HORNED COTTUS. 
177 
in the other species of the genus. Besides the superior 
and inferior supporting rays, this fin contains 11 other 
rays. The 8 or 9 middle ones, in old specimens at 
least, are generally branched, though one may sometimes 
find specimens from 130 to 140 mm. in length without 
a single branched ray in the caudal tin. In the male 
all the simple rays of this tin are generally rough 
throughout their length, but the branched rays, on the 
other hand, only from the beginning of the division to 
the tip: in the female on i v the uppermost ray is rough. 
When the caudal fin is folded up, the outer rays are 
generally those which extend farthest back. 
On the effects of difference of sex on the external 
parts of the body we find no remarks in any author 
before Ekstrom, although they are very striking. In 
the males the body is generally more cylindrical, and the 
beginning of the anal tin usually in front of the middle 
of the body. In these respects, as in several others, the 
males have retained their position in the juvenile stages 
of development, which they thus hold in common with 
the younger females; while we find that in very old 
males the anal fin sometimes begins a little behind the 
middle of the body, though not so far back as in fe- 
males of equal size. The males generally have also 
higher anal and dorsal fins and longer pectoral and 
ventral fins. This prevails in some cases, perhaps in 
most, to such an extent that the rays of the second 
dorsal fin, when depressed, extend beyond the base of 
the caudal fin; and it is a rule, to which we have found 
few exceptions, that in the males the length of the vent- 
ral fins is greater than that of the lower jaw. There is 
also a difference according to sex in the relations of the 
dorsal fins to each other. In the males the base of the 
second dorsal fin is generally longer than in the females, 
but the distance between the beginnings of the two fins 
is less. Though these two differences are not invariable, 
the rule holds good if they are combined, — attention 
being paid to the significance of the above-mentioned 
changes of growth — that in the males the distance 
from the beginning of the first dorsal fin to that of the 
second is less than the length of the base of the latter 
fin, while in the females , except during youth, it is 
greater. In the latter, too, the belly is more pendent, 
the anal fin begins behind the middle of the body, and 
the fin-rays are shorter and not so rough. In the 
following table we give the most important differences 
depending on age and sex which avc have found in 
eight females and five males: 
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I Length of the body in millimetres ___ _ 
73 
77 
78 
137 
173 
206 
218 
274 
162 
170 
256 
265 
272 
76.0 
201.5 
225.0 
,, ,, ,, head in % of the length of the body 
30.i 
31.2 
28.2 
29.5 
29.4 
29.3 
29.3 
33.2 
28.4 
30.o 
31.2 
29.4 
30. o 
29.8 
30.1 
29.8 
,, ,, maxillary bones „ ,, ,, ,, ,, ,, __ 
10.9 
11.7 
ll.i 
12.4 
12.i 
11.9 
12.4 
15.3 
11 7 
12.7 
14.o 
12.i 
15.i 
11.2 
12.8 
lo.i 
„ „ „ lower jaw „ „ „ „ „ „ „ „ 
15.2 
14.5 
15.2 
16.o 
15.o 
15.8 
14.8 
17.5 
15.4 
14.9 
14.8 
17.o 
17.2 
14.9 
15.s 
15.9 
,, ,, ventral tins .. ,, ,, ,, 
12.3 
13.o 
11.5 
14.6 
12.4 
10.8 
14.4 
13.5 
19 l 
17,i 
18 3 
17.3 
3.8 
26.i 
12 3 
13.i 
3.8 
19 6 
Least depth of the tail „ „ „ „ „ „ „ „ 
3.9 
4.o 
O.B 
3.6 
4.o 
3.9 
4.i 
3.6 
4.3 
3.5 
4.1 
4.o 
3.9 
3.9 
Distance from the anal fin to the tip of the snout in % of the length of the body 
Distance from the beginning of the first dorsal fin to that of the second in 
48.2 
48.i 
46.i 
51.5 
50.9 
52.i 
53.2 
55.6 
47.2 
48.o 
47.6 
50. o 
51.8 
47.5 
52.7 
48.9 
% of the base of the latter. - 
87.5 
95.6 
106.4 
107.4 
110.3 
118.5 
109. o 
110. o 
91.2 
94.6 
94.5 
92.6 
92.8 
96.5 
111.0 
93.i 
Least depth of the tail in % of the length of the longest ray in the anal fin 
40. o 
47.0 
47.6 
35.7 
46.6 
42.i 
37.5 
34.5 
38.8 
27.3 
28.7 
31.8 
22.o 
44.9 
39.3 
29.7 
„ „ „ „ „ „ ., „ „ „ „ ,, ,, „ „ „ second 
dorsal fin .. 
- 
35.o 
32.6 
36.6 
22 7 
33.3 
30.8 
28.i 
27.0 
19.o 
15.4 
18.7 
21.8 
13.3 
34.7 
28.4 
17.6 
Length of the ventral fins in % of the length of the belly from the insertion 
of these fins to the beginning of the anal fin 
51.4 
54.i 
46.4 
52.6 
44.8 
41.3 
50.8 
46.2 
79.5 
66.o 
73.4 
65.7 
100. o 
50.6 
47.i 
76.9 
Length of the ventral fins in % of the distance from the beginning of the 
/ 1st dorsal fin to that of the 2nd 
64.3 
65.3 
54.2 
69.0 
57.3 
46.4 
64.3 
61.i 
100. o 
82.8 
90.4 
81.4 
131.5 
61.3 
59. g 
97.2 
Length of the ventral fins in % of the distance from the anal fin to the tip 
of the snout 
25. g 
27.o 
25.0 
28.3 
24.4 
20.7 
27.i 
24.2 
40.5 
35.6 
38.5 
34.8 
50.4 
25.9 
24.9 
40. o 
Longest ray in the 1st dorsal fin in % of the distance from the beginning 
of the 1st dorsal fin to that of the second 
40. o 
50. o 
33.7 
34.5 
41.3 
35.4 
34.7 
40.5 
60.o 
54.3 
55.7 
53.o 
81.5 
41.2 
37.3 
60.9 
Longitudinal diameter of the eyes in % of the length of the head... 
18.2 
20.8 
22.7 
17.2 
23.5 
22.8 
17.2 
12.i 
24.0 
16.6 
15.0 
14.7 
14.7 
20.6 
18.6 
17.o 
Least breadth of the interorbital space in % of the least depth of the tail. 
96.4 
84,o 
(56.7 
100. o 
75.7 
87.5 
100. o 
145.0 
57.i 
113.3 
133.3 
114.3 
127.3 
82.4 
101.6 
109.1 
Scandinavian Fishes. 
23 
