158 
ZOOLOGY, 
utter a more distinctly musical sound than any other of 
those observed by Abbot, who states that "\t is a single 
note, frequently repeated, and has a slightly metallic reso- 
nance." It should also be noticed that the organs of hear- 
ing in many musical fishes are said to be unusually well 
developed, hence these sounds are probably love-notes; and 
Abbot notices the fact that these fishes are dull-colored 
during tlie reproductive season, as well as at other times, 
while voiceless fishes, such as the perch, common sun fish, 
chub, roach, etc., are highly colored during the breeding 
Fig. 202.— Gizzard Shad. 
season, and thus the sexes are mutually attracted in the 
one case by music, and in the other by bright colors. 
Finally, the sounds of fishes may be compared with those 
of reptiles, birds and mammals, the air-bladder correspond- 
ing to the lungs of the higher Vertebrates, while the pneu- 
matic duct is comparable with the trachea of birds and 
mammals. 
In swimming, the propelling motion is mainly exerted 
by the tail, the movements of which are somewhat like 
those of an oar in sculling. The spines of the tail-fin are 
movable, and are capable of being brought into such a 
position that the fin will meet with less resistance from the 
