136 



THE INTEGUMENT 



Such scales are fundamentally the same in origin as the teeth of 

 these fish, and are similar in origin to the teeth in higher verte- 

 brates. Three other general types of scales occur among fishes, 

 namely, ganoid, cycloid, and ctenoid scales. These are products 

 formed in pockets of the corium alone, without marked modification 

 of epidermal covering. 



In the skin of the bass many overlapping ctenoid scales project 

 above the general level of the epidermis. The epidermis which is 

 carried out with these plate-like projections is composed of stratified 

 squamous epithelium with a basal layer of cuboidal cells and several 

 intermediate layers of progressively more flattened cells until the 

 superficial layer of squamous cells is reached. (Fig. S2.) The 



Epidermis 



Skeletal muscle 



Fig. 82.— Diagram of integument of the bass, showing epidermis extending over 

 and between the overlapping scales. The scales are embedded in dense fibrous 

 connective tissue of the corium and above the skeletal muscle shown in longitudinal 

 section. 



epidermis rests upon a thin membrane of loose fibroelastic con- 

 nective tissue which separates it from the scales and the underlying 

 very dense fibrous portion of the corium. The epidermis takes no 

 part in the scale formation and is thinner where it folds under the 

 projecting scale. The scale is basally embedded in the dense 

 fibrous connective-tissue region of the corium, where its outline is 

 serrate. Above this region it is surrounded b>' the loose connective 

 tissue separating it from the epidermis. Chromatophores occur in 

 this loose connective tissue closely surrounding the scales. The 

 scales are formed bv the activity of osteoblasts derived from the 



coruun. 



INTEGUMENT OF AMPHIBIA. 



The skin of amphibians is usually soft and nu)ist and carries no 

 scales. The epidermis is characterized by a stratified epithelium 

 through which lunnerous nnilticellular alveolar mucous glands open. 

 (Fig. 83.) The individual surface cells are not desquanuited, but 

 there is a periodic shedding of large patches or sheets of cells of the 

 corneum. The corium is thin and may be separated by lymph spaces 



