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. leiurus, a naked kind ; but 

 the Swedish ichthyologists, Fries and Eckstrom, satisfied 

 themselves that these were one and the same, G. leiurus 

 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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