TELEOLOGY OF THE SKELETON OF FISHES. 155 



may live. You may witness the tactile action of the pectoral fins 

 when gold fish are transferred to a strange vessel : their eyes are so 

 placed as to prevent their seeing what is below them ; so they compress 

 their air-bladder, and allow themselves to sink near the bottom, which 

 they sweep as it were, by rapid and delicate vibrations of the pectoral 

 fins, apparently ascertaining that no sharp stone or stick projects up- 

 wards, which might injure them in their rapid movements round their 

 prison. If the pectorals are to perform a special ofiiceof exploration 

 certain digits are liberated from the web, and are specially endowed 

 with nervous power for a finer sense of touch, as we see in the gur- 

 nards, where they compensate for the loss of the tactile property con- 

 sequent on the hard covering of the exterior of the mouth in these 

 mailed-cheeked fishes {Jones cuirassees, Cuv.) 



Certain Lophioids living on sand-banks that are left dry at low 

 water, are enabled to hop after the retreating tide by a special 

 prolongation of the carpal joint of the pectoral fin, which fin in these 

 'frog-fishes' projects like the limb of a terrestrial quadruped and 

 presents two distinct segments clear of the trunk. 



The sharks, whose form of body and strength of tail enable them 

 to swim near the surface of the ocean, are further adapted for this 

 sphere of activity and compensated for the absence of an air-bladder 

 by the large proportional size and strength of their pectoral fins, 

 •wdiich take a greater share in their active and varied evolutions than 

 they can do in ordinary fishes. 



The fiat-bodied Rays, equally devoid of an air-bladder, and with a 

 long and slender tail, deprived of its ordinary propelling powers, 

 grovel at the bottom ; but have a still greater development of the 

 hands, which surpass in breadth the whole trunk, and react with 

 greater force upon it in raising it from the bottom, by virtue of a 

 special modification of the scapular arch, which is directly attached to 

 the dorsal vertebr£B. 



Nor is the pectoral member restricted in length where its office, in 

 subserviency to the special exigencies of the fish, demands a develop- 

 ment in tliat direction ; the fingers of the Exoccetus or Dactijlopteriis, 

 are as long, and tlie AA^eb which they sustain as broad, as in the ex- 

 panded wing of the flying mammal. Everywhei'e, whatever re- 

 semblance or analogy we may perceive in the ichthyic modifications 

 of the Vertebrate skeleton to the lower forms or the embryos of the 

 higher classes, we shall find such analogies to be the result of special 

 adaptations for the purpose or function for which that part of the fish 

 is designed. 



The ventral fins or homologues of the hind-legs are still more 

 rudimental — still more embryonic, having in view the compari- 



