Great Britain Natural History. 99 



or soft-bodied animals, commonly known as shellfish, constitute a most important class in the 

 economy of fisheries, not merely in their providing adult fish with food, but also as some of 

 them breed at the same period of the year, their eggs and microscopic young are useful as 

 aliment to the fish fry. Some forms are likewise more directly employed by man as food 

 and bait, as oysters, mussels, cockles, and periwinkles. The consumer needs no reminder as 

 to how scarce the first have become ; and along the east coast of Scotland mussels for use 

 as bait are attaining famine prices, while the belief appears to be almost general that there 

 mussel fisheries are retrograding. Many other forms of molluscs are much employed by line 

 fishermen for bait, especially whelks, squids, cuttle-fishes, &c. Among the marine Echine- 

 derms, viz. sea-urchins, star-fishes, and the sea-cucumbers, Holothuridse, all assist more or 

 less in providing food for fish, while a species of the last is largely consumed as food in 

 China, where it is looked upon as a luxury under the name of " trepang." The true worms 

 or Annelides are indispensable to fisheries. They are divisible into the abranchiata, or gill-less 

 forms, which contain earth-worms and leeches, and the branchiata, or gilled kinds, which 

 include tube-worms and sand-worms, &c. The Annelids comprise many forms largely employed 

 as food for fish, and some, as the lob-worm, are very useful for bait ; others, as leeches, are 

 detrimental to fish. Insects have been said to be nature's most favoured creation, having 

 combined in them all that is beautiful and graceful, interesting and alluring, or curious and 

 singular in every other class of her (nature's) productions. They are placed by entomologists 

 in three great divisions, in accordance with whether they pass through a metamorphosis or 

 not, and if they do whether such is complete or incomplete. Many insects form food for 

 fishes in some stage of their existence, while others are very destructive to fish eggs. Crus- 

 tacea are most generally known as lobsters, crabs, shrimps, prawns, &c., and are variously 

 divided by different zoologists. All Crustacea are water breathers ; some having eyes placed 

 upon footstalks, while in others they are without stalks, being sessile or immovable. All 

 undergo successive moultings or changes of shell, at which times lost parts become renewed. 

 In the earlier stages of the lowei crustaceans, they emerge from the egg as a small body, having 

 a central eye and two pairs of limbs (so-called Zoea stage), while as they gradually attain the 

 adult stage new segments and new limbs appear. In their earlier stages Crustacea become 

 a most important article of food for fishes, while their adult forms are likewise esteemed by 

 the more predaceous kinds. The class of Amphibia comprises newts, frogs and toads, and in 

 some localities frogs play a not unimportant part in fisheries, as they not only devour the ova 

 but likewise the fry, while their own spawn in turn becomes food for fish, and a frog is highly 

 esteemed by many fresh-water fishes. Keptiles (or Keptilia), including tortoises, turtles, terra- 

 pins, snakes, lizards, crocodiles and alligators, are more destructive to fish than are the true 

 amphibians. The Chelonians are usually divided into the swimming turtles, the mud turtles or 

 soft tortoises, and the terrapins, and lastly tke land tortoises. Some of the snakes and serpent 

 are frequently found in fresh water, where they are inimical to fish ; while in the seas of hot 

 climates are the venomous water-snakes (Hydrophidae) ; these have a laterally flattened tail, 

 lead an aquatic life, and live mostly on fish. Crocodiles and alligators abound in the fresh and 

 brackish waters of hot countries and are large consumers of fish, but the form best adapted for 

 this pursuit is perhaps the gavial of India, which often attains to twenty feet in length, and is 

 a resident throughout the Indus, Ganges, Brahmaputra and Mahanuddi rivers. The gavial 

 possess a'long and slender snout with a narrow mouth, they toss captured fish into the air, 

 and as they descend catch them and swallow them head first. Among birds, as is well known, 

 not only are the swimming ones, as the gannets, cormorants, gulls and terns of our coast 

 largely destructive to sea fish, but the last two extend their range to inland waters, where, 

 however, the dabchicks, coots, moorhens, herons, &c., assist in depopulating fisheries. Among 

 mammals the whale and seal fisheries are of great importance commercially. The whales, 

 dolphins, and porpoises or Cetacea themselves destroy immense quantities of fish. So also do 

 the semi-aquatic or amphibious seals ; while the otter in fresh and brackish waters is a large 

 fish consumer, although in the east it appears mostly to prefer frogs. 



FRANCIS DAY. 



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