VERTEBRATE ANIMALS 147 
as the animal moves along, and of allowing the scales to 
move over each other with greater ease. Pupils will see 
how extremely well adapted are these scales to the purpose 
they serve. The fish is a cold-blooded animal, as we shall 
learn further on, and hence does not require a warm coverin g 
e.g. of wool or feathers: such a covering would not only be 
unnecessary but would greatly retard the movements of the 
animal. The scales furnish just the covering required, being 
light, flexible, and hard, and provide the fish with a closely 
fitting armour which protects it from injury. Running 
along the side of the body is a series of perforated scales 
Dorsal fir 
Caudal Fin | ENA 
a Caacee 
Ti (KG EOC OW é 
SSSR YEG RTECS 
EEO OOO ALU ACER 
SSG ZZ 
: Pelvic Fil pectoral Fin. 
Fig. 98.—T ypical Fish. 
known as the lateral line. It is from this region that the 
slime is poured out—the pores being connected with the long 
chamber or canal which secretes the mucus or slimy material 
The lateral line moreover acts as a sense-organ, being the 
seat of a large number of nerve-endings, which enables the 
fish to feel the slightest vibration and to realise the approach 
of danger. 
Fins and Tail. The fins fall naturally into. two groups 
viz: the paired and unpaired fins. The paired fins are the 
pectoral fins, situated on the breast immediately behind the 
opening leading to the gills, and the pelvic fins also 
situated near the under surface of the body and usually 
