90 Elementary Manual of Zoology. 
essential features of structure to be found in fishes. Specimens six or 
eight inches long are large enough for the students to dissect. 
Notice the characteristic flattened spindle-shaped body without neck 
and with the trunk passing imperceptibly into the tail, also the scales, 
which cover the body and lie upon each other like roof tiles. Make out 
the following..— 
(1) The large toothless extensile mouth, with enormous fleshy lips 
and two pairs of barbels, (W.B,—Teeth are present in 
the throat.) 
(2) The large eyes, which are without eyelids. 
(3) The nose pits, which consist of two little holes on either side 
situated in front of the eyes. Notice that the nose pits 
~ do not communicate with the mouth, and are not used in 
respiration. ; 
(4) The lateral line. This is a well-marked line running down 
either side of the body from the head to the tail. It is 
formed by the openings of a series of little tubes which 
are believed to be sense organs. 
(5) The large gill chamber on either side of the head, covered with 
a bony plate (Operculum). : 
(8) The anal and urinary openings, which are situated close to each 
other in the middle line below, in the posterior third of 
the body. The anterior opening is the anus. 
Locomotion in the water is chiefly effected by the action of the tail, 
which is supported by powerful muscles, but the fins also assist. The 
fins of the Mahseer are as follows :— 
(1) The dorsal fin. This is the large unpaired fin in the middle 
of the back, Notice how the front ray is converted into 
a large stiff spine. 
(2) The anal fin, This is the unpaired fin below, just behind the 
anus. 
(3) The paired pectoral fins, which are situated just below the 
gill opening on either side, They correspond to the front 
limbs in other vertebrates. 
(4) The paired pelvic fins. These are situated on either side of 
the ventral surface about the middle of the length. They 
correspond to the bind limbs in other vertebrates. 
Make a sketch of the fish from the side, and mark in the names of 
the structures noticed above. 
Lift’up the operculum and examine the gills. Observe that they 
consist of four leaf-like organs, each with a hole (gill slit) on either 
side of it communicating with the mouth, Notice the little horny pro- 
cesses (gill rakers) between the bony supports of the gills. 
