MOLLUSKS 



3880 



MOLTING 



The coat of mail that protects the oyster and 

 numerous other shellfish from the dangers that 

 surround them is secreted by the animal itself 

 and is composed of carbonate of lime, which 

 often has the marvelous iridescent shimmer of 

 the rarest gems. The pearls found in the pearl- 

 oyster are notable examples; the spiral conches 

 cast up by the tide on beach or mud flat show 

 us that many of the humble mollusks dwell in 

 colored houses of more brilliant splendor than 

 any palace decoration. The bodies shut within 

 seem to have a rudimentary structure, but they 

 exhibit, in reality, well-developed systems of 

 nerves and circulation. One of the distinguish- 

 ing marks of the mollusk is the fact that it uses 

 a lung in breathing a mere sac, to be sure, but 

 still a lung. This is decidedly inconvenient 

 for such mollusks as live in the sea, for they are 

 obliged to come to the surface occasionally to 

 breathe, while their neighbors, the fish, are 

 equipped with gills that enable them to take 

 the oxygen they need directly from the water. 



Mollusks are, on the 'whole, rather sluggish 

 creatures, which accounts for the habits of the 

 oyster and the clam. The oyster, for example, 

 which is active enough when young, soon at- 

 taches itself to a rock and spends the rest of 

 its life in ease, waiting for the tides to bring it 

 the food it needs. The clam is hardly more en- 

 ergetic. It is found in great numbers burrow- 

 ing in the sand and mud along the seacoasts. 

 Sometimes the clam digger spies its back thrust- 

 ing up through the mud, when the tide is out. 

 The soft-shell clam, which is easily the aristo- 

 crat of its family, digs itself in to a depth of 

 a foot or more. It is conveniently provided 

 with flexible tubelike projections, called si- 

 phons, which it thrusts up through mud and 

 sand to the surface, sucking down both food 

 and air. 



Mollusks having two shells, like the oyster, 

 are called bivalved; while snails, which have 

 but one shell, are said to be univalved. 



Related Subjects. A detailed knowledge of 

 the most important species of these shellfish may 

 be gained from a study of the following articles : 



Argonaut 



Chitons 



Clam 



Conch 



Cuttlefish 



Gastropod 



Limpet 



Mussel 



Nautilus 



Octopus 

 Oyster 

 Scallop 

 Sea Lemon 

 Sea Squirts 

 Slug 

 Snail 

 Squid 



MOLOKAI, mo lo kah' e, one of the Hawaiian 

 group of islands, noted principally for its colony 



of lepers. The island is about thirty-five miles 

 long and eight miles wide, and has an area of 

 261 square miles. The climate is healthful and 

 agreeable. Lepers from all parts of the islands 

 are sent there by the government, where they 

 are completely separated from the healthy in- 

 habitants. The leper colony is governed chiefly 

 by members of religious Orders of the Roman 

 Catholic Church, who nobly give their services 

 in administering to the spiritual and temporal 

 needs of these unfortunate people. The most 

 prominent among them was Father Damien, 

 who after sixteen years of self-sacrifice died a 

 victim of the disease. The children of the 

 lepers are cared for in an asylum on the island 

 of Oahu. Politically, Molokai is a part of the 

 territory of Hawaii (see HAWAII). Population, 

 1910, 2,112. 



MOLT 'ING, the process by which Mother 

 Nature has arranged that birds and beasts may 

 shed their old skins, feathers, shells, hair, claws, 

 beaks or horns, and develop them anew. This 

 change is, of course, for the creatures' protec- 

 tion, since these parts of their bodies are gradu- 

 ally worn out through use, or become in some 

 way unfitted for their needs. On sonxe insects 

 and reptiles, such as spiders and snakes, the 

 outer covering, instead of increasing gradually 

 in size, renews itself completely at certain inter- 

 vals. An inner layer of cells secretes a fluid 

 which hardens, protecting the newly-exposed 

 body, at the same time shutting off nourishment 

 from the old skin, which dries and hardens, 

 finally dropping away. Birds shed their plum- 

 age once or twice a year, and often three times, 

 each complete molt taking from four to six 

 weeks. The feathers fall out one after another 

 in regular sequence, and there is a correspond- 

 ing renewal of their plumage; the birds, there- 

 fore, with few exceptions, are not prevented 

 from flying at such times. The first molt of 

 the season renews the bird's bedraggled winter 

 plumage ; the second decks it out for the mating 

 season. 



Some mammals, the highest order of animals, 

 shed their hair once a year, usually in the 

 spring; some of the deer family drop their 

 antlers also at that time. Other creatures whose 

 molt is somewhat extraordinary arc the lem- 

 mings, animals similar to the guinea pig, and 

 the ptarmigans, both of which drop their claws ; 

 while birds of the auk family shed the horny 

 parts of their bill (see AUK). Caterpillars usu- 

 ally molt five times before becoming butterflies. 

 See METAMORPHOSIS; also BIRD, paragraph 

 "Molting," under subhead Feathers. 



