ORIGIN OF THE LAND VERTEBRATES 93 



Besides the tail and the less important median 

 fins upon the back and belly, fishes possess paired 

 front and hind limbs, the pectoral and pelvic fins, 

 which are certainly the forerunners of the arms and 

 legs of terrestrial Vertebrates. These paired fins of 

 the fish do not however resemble in any detail the 

 limbs of the land animals. They are flattened 

 structures with either a short and broad, or long and 

 segmented axis to which are attached numerous rays 

 serving to stiffen the membrane of the fin. They are 

 of course used as paddles to propel the animal 

 through the water or, where the tail and body give 

 the chief motive force, to serve as guiding rudders. 

 There are several cases of fishes which have accessory 

 locomotory structures to enable them to jump on dry 

 land, to creep over rocks, and even to climb trees. 

 The little goggle-eyed fish, Periophthalmm, jumps 

 about on coral reefs out of the water, by means of 

 flicking its pectoral fins ; some Gurnards (Trigla) 

 can creep about on the sand by means of certain 

 finger-like rays on their pectoral fins ; the climbing 

 perch of Ceylon, Anabas scandens, can progress on 

 dry land and ascend trees by helping itself along 

 with spines growing out from its gill covers ; but 

 none of these structures have any more bearing on 

 the acquisition of the land Vertebrates' limbs, than 

 the fins of a flying-fish have on the derivation of the 

 wings of a bird. 



