322 



Recherches sur les Poissons Fossiles. 



shells, etc., upon the consideration of which we are more 

 particularly engaged, and which we are about to compare 

 with each other. 



The rete malphigii, as it is commonly called, is the inner 

 lamina of the epidermis which is not yet become hard, which 

 adheres to the corion, and which is at first soft, and after- 

 wards hardened by means of a secretion from the corion. 



The corion, in short, is the living part of the skin ; it 

 is formed of very hard mucous tissue, and of vessels and 

 nerves ; it adheres to the muscles by cellular tissue more 

 or less strong. It is this part of the skin which is the seat 

 of sensation, because of the number of nervous fibres which 

 it receives ; it is this which, by means of the net of little 

 sanguineous vessels with which it is covered, secretes the 

 coloured pigments at its surface, produces and supports 

 the other laminae of the skin ; and, in one word, which re- 

 gulates all the various functions of the surface of the body. 



The different tints of the skin are owing to the deposition 

 of different coloured pigments which float between the epi- 

 dermis and the corion. In those fishes in which they are 

 most abundant, we observe first at the inferior surface of the 

 scales, abed of pigment of a metallic golden or silvery aspect, 

 and which often produces various brilliant metallic reflec- 

 tions; (it is with this material that false pearls are coloured ;) 

 besides this, they have towards the surface of the back, and 

 in general on the upper parts of the body, numerous scattered 

 points, of various pigments, more or less approaching to a 

 black colour, which follow in such abundance, as to produce 

 on the skin the effect of paint. These different pigments 

 are composed of little crystals of different earthy and me- 

 tallic substances. They are found again on the external 

 surface of the peritoneum, on the brain, medulla oblongata, 

 and in the eyes. Ehrenberg observed them in the Pike, but 

 they exist in all fishes, and present numerous varieties of 

 form and composition according to the species. A very re- 



