BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 24. AFD. IV. N:0 8. 35 
naturally due to a greater size of these parts for holding 
the eggs. OC. gobio thus represents here the adult stage, 
which in this case is a female stage, OC. poecilopus represents 
the male- and juvenile stage. 
'The distance between the anal fin and the insertion of 
the ventrals. 
| C. poecilopus. | OC. gobio. 
| | | 
[5 45,21 57,5) 76,1) 42,51 57,9) 75,5 
"19 | 48,4| 62,7| 76,1) 42,4/ 58 |75,8 
Distance between the anal fin and the in- | | 
sertion of the ventrals in z of the length [3] 22,8] 21,9] 23,4] 24,2) 24,7) 24,7) 
FR RGRDGE VA oc Frej be öyjeloen sl are me E i | NS 
| 12 22,8) 22,4] 22,7) 24,7| 25,0] 26,1] 
Length of the body in millimetres . 
In this measurement, which is that of the belly, we find 
a peculiar difference between the forms. In C. gobio the 
measurement increases regularly as shown in the table above, 
the increase hardly perceptible in the males hut more notice- 
able in the females, in which also this distance is greater 
than in the males. On the other hand, in C. poecilopus we find 
at first a decrease in the measurement, but later on a change 
in the course of development, this measurement increasing in 
the more adult stage of C. poecilopus, without attaining that 
observed in the juvenile stage of OC. gobio. Another pecu- 
liarity 1s that the distinct difference in sex which appears 
in C. gobio is totally wanting in OC. poecilopus, and it is 
very probable that this sexual difference did not, to any ex- 
tent at least, occur in the parent form: it seems to be a 
character acquired by OC. gobio alone. 
It seems as if the two branches in this respect developed 
at first in opposite directions. In OC. gobio the measurement 
increased, in OC. poecilopus it diminished. While the former 
continued the direction followed from the beginning, the latter 
at a later period changed its course, following that of C. go- 
bio, which course was probably that of the primitive type. 
This delay in the course of C. poecilopus might explain the 
fact that this measurement is so much less in C. poecilopus 
than in OC. gobio. 
