XXVI INTRODUCTION. 



malformation in the human subject is that which is usual- 

 ly termed the hare-lip; the divided lip, and imperfectly 

 closed palate, representing the state of these parts in some 

 species of mammalia of a lower grade of organization than 

 man. In the case of the malformations in fishes here alluded 

 to, the deficiency appears to have arisen from an arrest of the 

 formative process at that point in which the shortened state 

 of the upper jaw resembles the rounded upper part of the 

 mouth in the Lampreys, a grade in structure preceding that 

 of the bony fishes. 



The unclosed state of the bones of the head in the human 

 infant, which are not firmly united till some months after 

 birth, is a permanent condition of the cranium in some rep- 

 tiles and fishes, as noticed and figured at page 380. 



Wounds in fishes heal rapidly ; and they appear to have 

 but few diseases, probably owing to the uniformity of the 

 temperature in the medium in which they reside. 



As previously stated, the food of a very large proportion 

 of fishes is of an animal nature, and they feed to a great 

 extent indiscriminately upon one another. From their ex- 

 traordinary voracity, their rapid digestion, and the war of 

 extermination they carry on among themselves, the greater 

 and more powerful fishes consuming the smaller and weaker, 

 from the largest to the most diminutive ; add to this, the 

 constant and extensive destruction effected by the numer- 

 ous sweeping nets of ruthless man, and it is even probable 

 that comparatively but few fishes die a natural death. 



