BRITISH FRESH-WATER FISHES 
dorsal. The tail bears the caudal fin. On the lower 
part of the body there is the pectoral fin behind the hind 
portion of the gill-covers, the ventral fin is right at the 
base of the belly, and the anal fin is situate where the 
body perceptibly narrows towards the tail. ‘The position 
of these fins varies in certain kinds of fishes, and this will 
be referred to when we are considering our own fresh- 
water species individually, but it will be as well to set 
out the uses of the fins just described. I have not read 
a better account of these than appears in one of Mr. W. 
J. Gordon’s useful Handbooks, and I feel sure he will 
allow me to repeat what he has written in his excellent 
book “Our Country’s Fishes.” Mr. Gordon says: 
“The caudal fin is the fish’s main propeller, with the 
paired fins he retains his trim, and the dorsal and anal 
he uses as a keel to keep him straight on his course. 
With his tail he does most of his steering, but he brings 
in his pectorals to help him. A stroke of the tail to 
starboard and a stroke or two with the starboard pectoral, 
with the port pectoral held against the body, sends his 
head to port; a stroke of the tail to port with a stroke 
or two of the port pectoral, and the starboard pectoral 
held in, sends him round to starboard; in fact the 
pectoral thrown out of action serves as a pivot on which 
he turns. Cut off a pectoral and he falls on the opposite 
side ; cut off both and his head sinks; cut off all his 
fins and he capsizes, owing to his upper half being the 
heavier.” 
Some fishes have the eyes to the left, others to the right. 
£6 
