THE CARP FAMILY. 169 



It occasionally happens to the angler to catch pearls 

 ready-made. These are found in the large river-mussel, 

 which, as is well known, will not unfrequently swallow a 

 worm or other ground-bait, taking so fast a hold with its 

 shell-lips as to be fairly hoisted out of the river's bed 

 and basketed. An instance recently occurred near Tweed 

 Mill, Coldstream, where a boy, who was worm-fishing for 

 Trout in the Chapel brook, caught a mussel 4 inches long 

 and 2 broad containing no less than forty fine pearls of 

 different sizes, some of which were thought to be worth 

 ten shillings each. 



It has several times happened to me to take mussels 

 whilst fishing ; but, either owing to my want of luck, or 

 lack of inquisitiveness, I have hitherto discovered nothing 

 in them more valuable than mud. There is another spe- 

 cies of mussel, never, I believe, found on these shores, 

 called the " Nacre," from which mother-of-pearl is pro- 

 cured; this shell-fish grows to the length of 2 feet, and, 

 according to Oppian, enters into copartnership with a small 

 species of crab, which permanently resides within its shell, 

 and in return for this lodging-accommodation caters for 

 the ' board ' of both parties. 



Most fishermen will have, on occasions, remarked Bleak 

 swimming round and round in circles with their heads 

 above the surface of the water, as if suffering from vertigo. 

 These gyrations are caused by thin white tapeworms, 

 sometimes as much as 9 or 10 inches long and three-tenths 

 of an inch wide, which get into the intestines of the fish, 



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