FISHES. 267 



CHAPTER II. 



EXTERIOR OF FISHES. 



The fishes, having no neck, and their tail at its commencement being 

 generally as large as the trunk, their body is most commonly of a 

 shape that only diminishes very gradually towards each of the extre- 

 mities, unless one or the other should be truncated or ended in a club, 

 or the tail (as occurs only in the rays) be much more slender than the 

 rest. 



The body is either rounded, as in the Diodons, or cvlindrical as in 

 the Eels ; it is compressed either horizontally as in the Rays, or ver- 

 tically as in the greater number of fishes. 



The head is either bulkier than the body, as in the genus Lophius, 

 or smaller, as is the case in many species ; it is round or compressed in 

 various directions; it is obtuse as in the Bull-heads (Cottus), or more 

 or less elongated as in the Flute Mouths (Fistularia), or the genus 

 Centriscus. There are fishes with the two jaws prolonged into a 

 beak as in the Gar Fish (Belone), and some with only the lower jaw 

 prolonged, as the subgenus Hemiramphus; or sometimes the upper 

 jaw forms a snout projecting over the mouth as in the Rays, the 

 Sharks, and the Sword Fish. 



The mouth opens either beneath the snout as in the Rays, or at its 

 end as in the greater part of fishes; it may open even vertically 

 towards the heavens as is the case with the Star Gazers (Uranoscopus) ; 

 its cleft is more or less extensive, varying from the size of a small hole 

 as in Centricus, to that of a vast mouth as in Lophius. 



Externally we only find the organs of two senses, the orifices of the 

 nostrils and the eyes ; the first are either very simple as in the Rays 

 and Sharks, or they are double as in the greater part of osseous fishes: 

 they may be more or less approximated either from the jaws, from the 

 eyes,or the end of the snout. 



The eyes vary extremely in size according to species, and they even 

 disappear occasionally under the skin, as in the Ribband Fishes 

 (Taenioides) : their direction is not less variable than their diameter ; 

 they are most frequently directed laterally, and are elevated some- 

 times so much, as to be completely vertical and turned to the 

 heavens, as in the Uranoscopes ; in the whole of the Flat Fishes 

 (Pleuronectes), they are both on the same side of the head, the right 

 or left. 



There is only one family of fishes belonging to theChondropterygians, 

 with the outer borders of the branchiae attached to the skin, and with 

 as many openings for the issue of water as there are intervening 

 spaces between the branchiae ; but all the other fishes of this order 

 have the branchiae free at the external border ; and the water which 

 they imbibe makes its exit by a single opening (a solitary gill) on 

 either side. This gill varies considerably in size and in the extent of 



