BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 24. AFD. IV. N:0 3. 21 
My measurements in the above table show that the length 
of the head from the tip of the snout to the tapering point 
of the gill-cover is about !/1 of that of the body, and that 
it is somewhat greater in C. gobio than in C. poecilopus. 
With age comes a regular increase in the size of the head, 
this increase being greater in the males than in the females 
and especially so in OC. poecilopus, of which latter in the 
females the length of the head is always in the same pro- 
portion to that of the body. 
In respect of the length of the head, C. poecilopus seems 
to retain more of the primitive state than OC. gobio, which 
latter has undergone a development, as also the male of 
C. poecilopus has begun to do. The sexual character, pro- 
bably existing already in the male of the original form, seems 
to have caused an increase of the length of the head in some 
specimens, which began thus to differ from the primitive type. 
At a later period these still farther advanced towards C. go- 
bio, while the others have remained in a more primitive state 
and thus have produced a form with small heads. 
Examining the anterior and the posterior parts of the 
head,! we find just the same state of things; in the adult 
males of C. poecilopus these parts are considerably longer 
than in the females, which latter retain the juvenile form, 
especially noticeable in the anterior part of the head. "This 
character of the poecilopus-male is still more developed in 
C. gobio and especially in the males. As with the poecilopus- 
female so the gobio-female also retains more of the juvenile 
stage, especially noticeable in the anterior part of the head. 
The same course of development appears more or less dis- 
tinetly in the snout (the distance between the anterior mar- 
gin of the eye and the tip of the snout), and in the inter- 
orbital breadth, being the distance between the globes of the 
eyes (not the least breadth of the frontal bone), and in the 
greatest depth of the head. 
The longitudinal diameter of the eye shows no difference 
in the two sexes, for which reason it is impossible to speak 
of any influence of one or the other sex in the development 
1 The anterior part is the distance from the tip of the snout to the 
hind margin of the preopercle (the base of the preopercular spine), the pos- 
terior part is the distance from the hind margin of the eye to the posterior 
point of the gill-cover. 
