FISHES 



135 



creeps round to meet its fellow. When two months old 

 the fish has sunk to the sea-bed to take up a one-sided view 

 of life, the undersurface of the body being denied light 

 remaining white whilst the reverse side becomes pigmented. 

 The Globe or Puffer Fishes (Tetraodon) have the power 

 of inflating themselves until they become spherical in 

 shape. The skin when blown out becomes distended 

 and stretched tight and the double-rooted erectile spines 

 with which many of these fishes are covered act as for- 



Cow Fish 



midable weapons of defence and compensate their owner 

 for its indifferent swimming power. 



The Trunk and Cow Fishes (Ostracionidae) are likewise 

 very slow swimmers, and like the Purler Fishes rely on their 

 armour. In their structure these fishes recall certain primi- 

 tive fish of the old Red Sand Stone Period, the body being 

 encased in a perfectly rigid cuirass with the tail similarly 

 armoured and attached by a socket-like arrangement, 

 which permits very little movement, confining its functions 

 purely to that of a rudder. In the case of the Cow Fish 

 the popular title refers to the shape of the head, the bovine 

 appearance of which is accentuated by two prominent 

 hornlike structures one over each eye. 



