80 Fisiirs. 



the inferior anal, and the fin at tlie end of tlie tail caudal. The rays are 

 of two kinds ; the one consists of a single bony piece, usually hard and 

 pointed, sometimes flexible and elastic, divided longitudinally — these are 

 called spinous rays ; the others are composed of a great number of small 

 articulations, and are generally divided into branches at their extremity — 

 they are the soft, articulated, or branched rays. 



There is as much variety among Fishes, with respect to the number 

 of limbs, as among Reptiles. Most generally there are four; some have 

 but two, and in others they are totally wanting. The bone which is ana- 

 logous to the scapula, is sometimes held among the muscles as in the 

 higher animals, and at another time it is attached to the spine, but most 

 commonly it is suspended on the cranium. The pelvis rarely adheres to 

 the spine, and very frequently, instead of being behind the abdomen, is 

 before it, and connected with the humeral apparatus. 



The vertebrae of Fishes are united by concave surfaces filled with car- 

 tilage, which most generally communicate by a canal excavated in the axis 

 of the vertebrae. In most of them there are long spinous processes which 

 maintain the vertical form of the body. The ribs are frequently soldered 

 to the transverse processes. 



The head of Fishes varies more as to form than that of any other class, 

 notwithstanding which it almost always consists of the same number of 

 bones as is found in other oviparous animals. The frontal bone is com- 

 posed of six pieces ; the parietal of three ; the occipital of five ; five pieces 

 of the sphenoid, and two of each temporal bone, remain in the composition 

 of the cranium. 



Besides the usual parts of the brain which are arranged as in reptiles 

 in a row, fishes have also knots or ganglions at the base of their olfactory 

 nerves. 



Their nostrils are simple cavities at the end of the muzzle, almost always 

 perforated by two holes, and regularly lined by a plaited pituitary mem- 

 brane. 



The cornea of their eye is very flat, and there is but little of the aqueous 

 humour; the chrystalline lens, however, is very hard, and almost globular. 



Their ear consists of a sac representing the vestibule, in which are sus- 

 pended small bodies most commonly of a stony hardness, and of three 

 membranous semi-circular canals, situated in the cavity of the cranium 

 rather than in the substance of its parietes, the Chondropterygii excepted, 

 in which they are entirely contained in them. The eustachian tube and 

 tympanal bones are always deficient, and the Selachians alone have a fe- 

 nestra ovalis, which is level with the head. 



The sense of taste in fishes can have but litlle energy, as a great por- 



