OF THE BRITISH ISLANDS. 67 



literally ripped open by the ventral spines of his opponent, 

 or is driven ignominiously from the field. It has been 

 observed that the victor in these combats immediately ac- 

 quires a far more brilliant hue than he previously possessed, 

 with an augmented display of activity and defiance in his 

 bearing. The vanquished, on the other hand, if he escapes 

 with his life, loses all his gay tints, and retires into 

 obscurity among the females and more peaceable members 

 of the shoal. 



The Three-spined Stickleback is remarkable for the great 

 number of sports or varieties into which it developes in 

 different localities, and in accordance with the nature of its 

 surroundings. Such varieties are manifested chiefly in 

 connection with the protective armature of vertical bony 

 plates developed along the sides of the body ; those affecting 

 a salt-water habitat, and thus being exposed to a greater 

 number of enemies, being the most completely armed, and 

 those confined to quiet inland waters being the least 

 protected in this respect. Dr. Day, in his ' Fishes of Great 

 Britain,' enumerates, in addition to the normal form, as 

 many as six such local varieties of this type, the majority 

 of which will be found in the spirit-preserved collection that 

 bears his name. These include the Rough-tailed Stickle- 

 back (G. trachiuriis), with from thirty to forty plates each 

 side, the Half-encuirassed Stickleback (G.semiloricatus), with 

 twenty-two or twenty-three vertical plates, the Half-armed 

 variety (G. semiarmatus), with ten to fifteen such plates, and 

 the Quarter-armed or Smooth-tailed Stickleback (G.gymnu- 

 rus), with from four to six shields only. The two remaining 

 varieties are the Short-spined form (G. brachyceutrus), with 

 very short dorsal and ventral spines, and the so-called Four- 

 spined Stickleback (G. spinulos -a), with a rudimentary fourth 

 dorsal spine developed between the two hindmost spines 



F 2 



