546 



ANATOMY OF VERTEBKATES. 



-sebaceous, sudoriparous, and mucous follicles may be developed 

 in or from the derm : the epiderm may be condensed into nails, 

 claws, hoofs, horns and horny scales. The warm-blooded are dis- 

 tinguished from the cold-blooded classes by the non-conducting or 

 heat-retaining nature of the superficial covering of the tegument. 



360 





Diagrammatic section of skin of flsh. 



99. Teguments of Fishes. The skin in fishes is more tensely 

 stretched over the body, and often more closely united to the sub- 

 jacent fascia or flesh, than in other Vertebrates : consequently it 

 enjoys less mobility. The constituent fibres of the derm or 

 corium are so disposed as to give it a laminated structure, fig. 

 360, a ; the horizontal layers being connected by vertical sub- 

 elastic fibres, 1 ib. b. The numerous papillae or processes from the 

 skin of the under part of the head of the Sole (Solea vulgaris) 

 give it a villous character : other instances where the derm deve- 

 lopes tactile papillae in fishes are indicated at pp. 326,411. 



In the Lancelet the dermal fibres are minute, and compacted 

 into two planes, one nearly at right angles to the other. In the 

 Lamprey the derm consists of two layers of flattened fibres cross- 

 ing each other at right angles. The epiderm exhibits numerous 

 large stellate pigment-cells. In the Eel, the epiderm is soft and 

 thick, consisting of many layers of cells, caudate and tessellate, 

 those next the derm showing pigment in stellar masses : the 



granular pigment-cells look like black 

 spots in the epiderm. On removing 

 this, narrow oblong scales, two lines 

 to three lines long, fig. 361, , are seen 

 imbedded in depressions of the derm. 

 They consist of a finely reticulate car- 

 tilage, the long axis of the meshes, 

 which may be cells with confluent 

 walls, running nearly parallel to the 

 contour of the scale, as shown in the 

 magnified section taken at the line marked in fig. 361, a. In the 

 Blenny (Zoarces) the skin presents circular depressions which are 



1 ' Arctuons bands ' of Clark (ccxcn, p. 148), who well distinguishes them from 

 the gland-ducts perforating the skin in certain fishes, e. g., murcena. 



361 



Scale of Ed : a, nnt. size, and portion 

 niagn. ccxcm. 



