FISHES. 351 



It also happens that the scalesof the inferior border of the belly being 

 compressed, trenchant, and united together, present a species of 

 external sternum, something in the form of a saw. This is seen in 

 the herrings, and the serra-salmons. 



The kind of integuments furnished by the scales being "well 

 adapted to facilitate natation by their smooth surface, and the little 

 resistance they present to the liquid, and also to preserve the fishes 

 from the clashings and friction to which they are exposed amongst 

 the rocks which stick out from the depths of the sea, is but a slight 

 garantee against the impression of the variations of temperature ; but 

 the heat of fishes not exceeding that of the element by which they 

 are surrounded, they have a less dread of cold than birds and qua- 

 drupeds ; it is for the same reason that reptiles are only covered with 

 scales or a naked skin. 



Subsequently added in a Supplement by the Author. 



Fig. VI. of the pi. vii. shows the silvered membrane, /., raised on 

 a part of the globe of the eye, to allow the clioroid to be seen, k, and 

 the vascular pad. 



Fig. VII. shows at c. the external lamina of the cornea, which is 

 a prolongation of the skin ; /. is the iris lined above by the silvered 

 membrane, and by the uvea below ; m. the choroid ; n. the ratinu ; 

 0. the vitreous body. a. the semicircular horizontal canal; b. the 

 anteaior vertical ; c. the posterior vertical ; d. the ampullae ; e. the 

 membranous vestibule; /. the sac ; y. the union of the two semi-cir- 

 cular vertical canals ; a. the varions branches of the seventh pair, 

 which proceed to''the ampulla and the sac. 



No. X. of plate viii. shows the four scales of the perch : a and b are 

 the large scales of the sides; c, a scale of the laternal line perforated 

 by a tube, and d, a scale of the back. 



Figure 2 of plate viii. and of figure 1 of plate vii. show in R the 

 natatory bladder. In the first it is in its right situation ; it is per- 

 ceived between the sides : in the second it has been, like all the 

 intestines, lowered, in order to show the kidneys, SS, and the urinary 

 bladder, T. Its sides are covered anteriorly with clusters of red 

 pencilled lines, and vessels which form them, and posteriorly by 

 the arteries which it receives from the deep-seated branches of the 

 intercostals and veins which unite with those of the ovary. 



It may likewise be added for the knowledge of figure 1 of plate A'ii., 

 that in the orbit are seen the ophthalmic nerve, 5-i the nerves of the 

 third pair, those of the fourth and sixth pairs ; that likewise is seen 

 the superior maxillary, 5-2, the inferior maxillary, 5-3, the opercular 

 nerve, 5-5, the nerves of the eight pair in 8, the last branch of which 

 is supported on the stomach in 8-i ; 9, 10, 11, and 12 are pairs of 

 nerves which go to the shoulder, arm, and pectoral fin : those of 

 the ventral fin are supplied by the branches of the intercostal : 13, 14, 

 15, in X, x-i, x-2, are the apertures of the anus, ovaries, r.nd bladder, 

 situated, as is seen, in fishes in an inverse position to that of other 

 vertebrae. 



It may be added that the figure 4 represent the testicles R, R, and 

 the bladder, Q ; that figure 9 shows an ovary cleft longitudinally to 



