64 THE STORY OF FtSH LIFE. 



fishing-frogs (Malthe) the pectoral and pelvic fins 

 are modified for walking on the sea-floor. 



The pelvic fins, like the pectoral, sometimes 

 have the rays drawn out into filaments to serve 

 as organs of touch, as in the " gourami " (Ospliro- 

 menus olfax), and the dwarf cod-fish Bregmaceros 

 of the Indian Ocean. Sometimes, as in the 

 Monocentris of Japanese waters, the ventral fin is 

 represented by little more than a stout bony 

 spine. In the lump-suckers of our seas, the 

 ventral fins are modified to form a sucking-disc. 

 This sucking -disc is very powerful, it being 

 exceedingly difficult to remove a fish from any 

 object to which it may have attached itself. In 

 the " gobies " the ventral fins also serve as a 

 sucker, but they have not so completely lost 

 their fin-like appearance as have the lump- 

 suckers. In the little sucker-fishes of our coast 

 (Lepadogaster) the ventral fins form the rim 

 only of the sucker, the rest being formed by a 

 modification of the bones of the shoulder-girdle. 

 If these fishes be caught with the hand they at 

 once attach themselves thereto by this sucker. 



We have now surveyed the principal facts 

 concerning the fins of fishes, and the modifica- 

 tions which they undergo to fit them to perform 

 new functions for which they were not originally 

 intended. The fact that these fins are capable 

 of modification is a very significant one, and 

 very naturally leads to the suggestion that this 

 adaptability may be traced in another direction, 

 and show us that the fins, normal fins, such as 

 we see in our type, the perch, or the salmon, may 

 themselves be but modifications of some earlier 



