THE TARPON 55 



The reason the tarpon is so rapid in the water is its sym- 

 metrical body and its deeply forked tail, which avoids the 

 space behind the axis of the body where the stream lines con- 

 verge after following the sides of the moving fish. 



The dorsal and anal fins can be folded into the body and 

 they are carried in this position when the fish is swimming 

 rapidly. This is done so the streamline form of the fish may 

 not be broken. They are extended when the fish desires to 

 slow down or tnrn. The paired pelvic fins maintain the sta- 

 bility of the fish while the pectorals aid it in slowing down or 

 changing direction. These fins are likewise folded while the 

 fish is proceeding at top speed. 



The mucous which the tarpon exudes from its body also 

 tends to increase its speed. 



The part of the anatomy of a fish which apparently is least 

 understood by naturalists are the lateral lines which extend 

 down the sides of the body and which every angler has ob- 

 served. If one will detach one of the scales on this line, clean 

 it in water, and hold it up to the light, it will be observed that 

 it is perforated by small holes. I understand it is partly 

 through them that the mucous is discharged which enables the 

 fish to swim more speedily, or, to put it in another way, to 

 slip through the water with greater ease. But the lateral line 

 system plaj^s a still more important part in the life of a fish. 

 Tubes underlie the scales and communicate with the exterior 

 by canals branching off from them and ending in pores. These 

 mucous tubes radiate widely over the body. Sense organs are 

 present which communicate with the brain. 



It is supposed that this complicated apparatus gives a 

 fish a sense of hearing and touch denied to other animals and 

 enables it to detect the presence of other fishes, its prey and 

 obstructions in its path. The precise functions of the lateral 

 line system is not fully understood, which is another illustra- 

 tion of the veil which nature has so cunningly thrown around 

 an animal so familiar as a fish and one which has been studied 

 since the dawn of history. 



