THE COLORATION OF FISHES. 339 
strikes strongest, and it tapers away to the under-surface, where the 
light does not directly strike at any time. Could it be that even 
if herring swam with theirgleaming sides uppermost it would matter 
much, or expose them more to the onslaught of enemies from above 
or below? Yet why is all the beauty and glamour on the sides? 
And ean any ordinary Darwinian reason be advanced for the glori- 
fication of a gregarious fish, that cannot now desire to do more than 
keep close to its brilliant neighbour, with the chance of escaping 
in the mélee, if attacked by the larger marine Carnivora? Yet it 
is a significant fact that when a herring is most on its own 
responsibility and engaged in the struggle for existence—in the 
gut-poke stage—it is least brilliant and least notable! This 
points, perhaps, more to the effect of rich feeding than to any 
other cause of brilliance, and we will find this determining cause 
also in other instances. Meantime, this brings us to the fourth 
cause of brilliance and colouring—sex selection, or the sentiment 
and excitation of sex. 
The idea of sex and its consequences, so vital as a ruling 
influence in the animal world, does not generally appeal to the 
ordinary intelligence as a matter of special importance amongst 
the finny tribe. Only where animals mate, whether as mono- 
gamists or polygamists, would sex be reasonably expected to 
exercise any special influence; and the fishes of commerce, at any 
rate, with the exception of the Rays (Raiide), are not under 
either category. But yet there is an interesting class of fishes 
that is amongst the highest in intelligence and the most charming 
in colouring of any in the temperate zones, which vie with 
terrestrial animals in attention to their mates, and care of their 
offspring up to a certain stage. The best known of this class of 
fishes is the little Stickleback (Gasterosteus), the male of which is 
so pugilistic, so be-crimsoned in the mating season, so careful in 
the construction of a nest, and so heroic in its defence. It has 
been so often described in this capacity that it is sufficient now to 
refer toit. But it is really only a type of the shore fishes. The 
Gunnel Fish (Centronotus gumnellus (Linn.)), with its row of 
brilliant spots along the dorsal edge, is monogamous apparently, 
and watches over its sickening mate and her walnut of expanding 
ova with attentive care. The Blennies (Blenniide) are another 
group that demands closer study in this connection, and so far as 
