THE STICKLEBACK 81 
The skin is silvery and without scales, but certain parts of 
it are protected by the extension of the skeleton into bony 
“scutes,” or armour-plating. The uncertainty which natural- 
ists have shown in classifying the sticklebacks has arisen in 
great measure from the variation in this armour, which is not 
only sometimes absent in specimens of the three-spined stickle- 
back from Central Europe, but changes with the seasons. Cuvier, 
for instance, distinguished two species—Gastrosteus trachurus, 
an armoured kind, and G. /eiurus, a naked kind; but 
the Swedish ichthyologists, Fries and Eckstrém, satisfied 
themselves that these were one and the same, G. J/eiurus 
being the creature in his gay summer attire, when the 
armour is discarded, and G. trachurus in the more sober winter 
colouring, when the fish is in full defensive panoply. More- 
over, they were able to show the armour in every stage of 
development. 
The chief normal armature may be described as consisting 
of lateral and pelvic plates ; the former protecting the pectoral 
region between the bony gill-covers and the pectoral fins, the 
latter beginning close behind the ventral fins and shielding 
the flank and part of the sides. The mouth of this fish is 
very small. 
In colouring, the stickleback is as variable as in the fashion 
of its armour. The back may be green, brown, or slate-blue, 
the sides and belly are silvery. The fins are delicately tinted with 
green, but not so deeply as to lose their transparency. The iris is 
silvern, and there is generally more or less red about the throat 
and breast, especially in the males. It is in spring that these 
are to be seen in full splendour, and truly theirs is no mean 
glory. What the kingfisher is among British birds, the male 
stickleback becomes in the breeding season among the fish of our 
lakes and streams—a creature of tropical lustre. As he swims in 
the shallow water the general effect is that of fiery red and opaline 
green ; his breast and throat are mantled with scarlet dye, and 
his sides shine with metallic lustre. Nor is all this fine array 
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