Professor Owen's Teleology of the Skeleton of Fishes. 225 



ascertaining that no sharp stone or stick projects upwards which 

 might injure them in their rapid movements round their prison. If 

 the pectorals are to perform a special office of 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 gurnards, 

 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 (Joues 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 pro- 

 longation 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 larger proportional size and strength of their pectoral fins, 

 which take a greater share in their active and varied evolutions than 

 they can do in ordinary fishes. 



The flat-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 vertebrae. 



Nor is the pectoral member restricted in length where its office 

 in subserviency to the special exigencies of the fish, demands a de- 

 velopment in that direction ; the fingers of the Exoccetus or Dacty- 

 lopterus, are as long, and the web which they sustain as broad, as 

 in the expanded wing of the flying mammal. Everywhere, whatever 

 resemblance or analogy we may perceive in the ichthyic modifications 

 of the vertebrate skeleton to the lower forms in 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 rudi- 

 mental — still more embryonic, having in view the comparison with 

 the stages of development in a land animal — than the pectoral fins ; 

 and their small proportional size reminds the homologist of the later 

 appearance of the hind-limbs in the development of the land Verte- 

 brate. But the hind-limbs more immediately relate to the support 

 and progression of an animal on dry land than the fore-limbs : the 



* Homologue, intimates the same organ in different animals under every va- 

 riety of form and function. Analogue, a part or organ in an animal which has 

 the same function as another part or organ in a different animal. 



