1898] Change of Functions in Fishes' Fins. 131 



developed. Iftheplevic fins in fishes really represent the legs 

 and feet of higher animals, while the pectoral fins are homolog- 

 ous with the arms and hands, the change of function described 

 is of great interest, for the hind limbs in this case have not only 

 lost their principal locomotor purpose, but have assumed the 

 complicated functions of the fore-limbs. Mr. H. Charles 

 Williamson, an able expert officer of the Scottish Fishery 

 Board, published in 1893 a thorough research upon the free fin 

 rays of the gurnard's pectoral fin, and described in detail the 

 bones, myology, and nerve supply in the finger-like rods of the 

 breast fins in that fish,* illustrated with nearly a hundred figures, 

 and his conclusion is that, in view of their abundant sensory 

 nerve supply, and the remarkable structure of their tips, and 

 apart from any mechanical uses they may have, the free rays of 

 the gurnard's fins are primarily extremely sensitive organs of 

 touch. Mr. Williamson points out that it is generally agieed 

 that the fin-rays in these cases are sensitive, " but one zoologist, 

 Deslongchamps,has maintained that they also have a mechanical 

 action. He had the opportunity of watching some gurnards, 

 which were confined by means of a net in shallow water. He 

 states that he observed the gurnards marching about on the fin 

 rays, and also stirring up sand by means of these structures. 

 Bloch, according to Tiedmann, suggested that the free 

 rays may be lures to attract prey." The use of sucli ra)'s as 

 lures, or for digging or other mechanical purposes is question- 

 able, when we find it proved that they arc extremely scnsiiive. 

 In the case of the Goose-fish {Lophius), which uses its breast fins 

 as legs, or the still more remarkable Jumping Goby of Ceylon 

 and Fiji we have a change of function scarcely inferior in 

 interest. Moseley describes the latter extraordinary fish as 

 follows : — " Hopping about on the mud, beneath the mangroves 

 on the (Fiji) shore was the PeriophtJialmus, at which I had often 

 been astonished in Ceylon. This little fish skips along the sur- 

 face of the water, by a series of jumps, of the distance of as much 



*iith Ann. Rep. Scottish Fishery Board, pp. 322-332. 



