TELEOLOGY OF THE SKELETON OF FISHES. 151 



remind the homologist of their condition in the imperfectly developed 

 skull of the embryos of higher animals ; but this condition is especi- 

 ally subservient to the peculiar and extensive movements of the jaws, 

 and of the bones connected with the hyoid and branchial apparatus. 



Not any of the limbs, properly so called, of Fishes, are prehensile ; 

 the mouth may be propelled and guided by them to the food, but the 

 act of prehension must be performed entirely by the jaws. Hence in 

 many fishes both upper and lower maxillary bones enjoy movements 

 of protraction and retraction, as well as of opening and shutting. The 

 firm connections of the upper jaw, and wedged fixity of the bone 

 suspending the under jaw, which characterise the higher Reptiles and 

 Mammals, would be imperfections in the Fish ; in which, therefore, 

 such characters are not only absent, but special development in the 

 opposite direction, not unfrequently, goes so far as to produce the 

 most admirable mechanical adjustments of the maxillary apparatus, 

 compensating for the absence of hands and arms like those which 

 have been exemplified in the instance of the Epihulus insidiator 

 (p. 108./^. 37.). 



"We must guard ourselves, however, from inferring absolute 

 superiority of structure from apparent complexity. The lower 

 jaw of fishes might at first view seem more comjilex than that of 

 man, because it consists of a greater number of pieces, each ramus 

 being composed of two or three, and sometimes more separate bones. 

 But, by parity of reasoning, the dental system of that jaAv might be 

 regarded as more complex, because it supports often three times, or 

 ten times, perhaps fifty times the number of teeth which are found in 

 the human jaw. We here perceive, however, only an illustration of 

 the law of vegetative repetition as the character of inferior organ- 

 isms ; and we may view in the same light the multiplication of pieces 

 of which the supporting pedicle of the jaw is composed in Fishes. 

 But the great size and the double glenoid or trochlear articulation of 

 that pedicle, are developments beyond, and in advance of the condi- 

 tion of the bones supporting the lower jaw in Mammalia, and relate 

 both to the increase of the capacity of the mouth in Fishes for the 

 lodgment of the great hyoid and branchial apparatus, and to the 

 support of the opercula or doors which open and close the branchial 

 chambers. The division of the long tympanic pedicle of Osseous 

 Fishes into several partly overlapping pieces adds to its strength, and by 

 permitting a slight elastic bending of the whole diinini.shes the liability 

 to fracture. The enormous size, moreover, of the tympano-mandibular 

 arch, and of its diverging appendages, contributes to ensure that pro- 

 portion of the head to the trunk which is best adapted for the pro- 

 gressive motion of the fish through the water. But witliout the 



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