ANALOGIES. VERTEBBATA TO CARTILAGINES. 155 



yet it is most extraordinary to observe the perfect regu- 

 larity with which they follow each other. Every zoologist 

 will confess the likeness between the sharks and the por- 

 poises, even in their external appearance : and while no 

 fish make such a near approach to quadrupeds as the 

 sharks, no quadrupeds more resemble true fish than the 

 Cetacea : this, of itself, is a fact so far beyond dispute, 

 that we may at once pass on to the next analogy. The 

 enormous pectoral fins of the rays, and the remarkably 

 small size of the others, which are nearly obsolete, in- 

 contestibly prove that in them is concentrated nearly 

 all the powers of locomotion, and accounts at once for 

 the excessive rapidity with which they swim ; this is 

 precisely the case with birds ; whose wings correspond 

 anatomically with the pectoral fins of fishes. The 

 very appearance of some of the rays shows that nature 

 intended to make them represent the feathered class ; 

 and this analogy is so apparent to ordinary observers, 

 that several have acquired the name of sea eagles, eagle 

 rays, &c. As the eels obviously represent the serpents, 

 so do the ChinKBridcB represent the reptiles, the pri- 

 mary external character of which consists in the tail 

 being excessively lengthened, and gradually ending in a 

 point. The Chirrn^ridcs are the only cartilaginous fishes 

 yet discovered, that have a tail thus formed ; and they 

 cannot, therefore, be likened to any of the vertebrated 

 divisions, excepting the reptiles. The analogy between 

 the sturgeons and the Amphibia is not only faint, but 

 even obscure. But this may be easily accounted for 

 in two ways : first, it is an indisputable fact that the 

 analogies between two groups of animals thus com- 

 pared, are almost always weakest between their most 

 aberrant types ; and secondly, because, when there are so 

 few species in a group, as in the SturionidtB, we have 

 not the same facilities or materials for determining its 

 analogies, as when it is more numerous : the points of 

 comparison, in short, are few; and setting aside the 

 ignorance under which we may labour, we must, in 

 all such cases, rest satisfied, if what is really known does 



