THE OYSTER-INDUSTRY. 223 



transparent glassy plates united at their edges. When the plant dies and the soft parts decay, this flinty skeleton 

 falls to the bottom, but is not destroyed. Century after century they accumulate and form immense beds, 

 contributing myriads of skeletons to the rocky mass. 



The green oysters of Europe. — The Diatoms are brown, when they possess any color at all. It is not duo 

 to them, therefore, but to eating the chlorophyltiuted spores or the whole plants of other species, that the 

 "greening" of oysters, or the "green-gill", is due. This has frequently been ascribed to some metallic absorption, 

 which rendered the oyster unlit to eat. I am, therefore, glad to be able to quote Professor Sullivan again on this 

 point. He says: 



As the n-reen color of the mantle of oysters from certain localities jnst referred to is commonly attributed to copper, and as siich oysters 

 are conseqiicntly believed very generally to bo poisonous, and their value therefore greatly depreciated, I made the most careful search for 

 traces of that metal in the nnids which I had received from grounds known to produce green-bearded oysters. Oysters and other mollusca 

 l)laccd in solutions containing copper and other metals absorb them, and retain them in their tissues. I have had two or three 

 opportmiities of examining oysters which had assimilated copper owing to miue-water containing it being allowed to flow into estuaries 

 at places close to oyster-heds. In every case the copper was found in the body only of the oyster, which it colored bluish green, and not 

 In the mantle or heard, which was not green. In the green-bearded oysters which I have had an opportunity of examining, the body was 

 not green, and no trace of copper could be detected in any part of the animal. The color, too, was not the same as that of the true 

 copper oysters, but rather that which would result from the deposition of chlorophyl or other similar chloroid vegetable body in the cells. 



In the oysters at Arcachon, France, a violet tint has been observed, sometimes, which is due to a similar cause, 

 although referred to the iodine and bromine of sea-water. Certain reddish algte were found, when washed in fresh 

 water, to impart to this a brilliant violet tint ; and by careful observation it was ascertained that even the spores 

 of these plants, which cou.stitute a not inconsiderable portion of the nutriment, were similarly colored. In ordinary 

 seasons, the dilution of the salt water by the rains in the Arcachon basin is sufficient to wash out the color of the 

 si)ores of the algiP, but when the brine is strongly concentrated, there is no such appearance about the gills of the 

 oyster as has been described. 



Rate of growth in oysters. — It is, of course, largely upon their supply of food and of lime that their 

 growth depends. This growth, however, is very variable, depending on the season, and in some years the increase 

 is very slight. In general, trans]>lanting young oysters in water similar to that in which they were born, causes 

 them to grow more rapidly ; but if they are carried into different temperature and other strange conditions, they 

 will grow slowly. Thus in New York bay, the East river, and Newark bay " seed" far outgrows that brought from 

 Virginia. In the Chesapeake, no doubt, the reverse would be true. But the conditions affecting growth may 

 vary greatly within the same district. At Bird island, in Boston harbor, for instance, bedded oysters grow but 

 very little, while those on the muddy shores of Winthrop, in fresher water, add a great length to their shells, 

 but improve very little in flesh, making them very profitable to sell by the barrel, but not to' open. 



Effect of weather. — The weather affects their health somewhat. When heavy winds blow in from the sea, 

 making high tides and cold, salt water, the oysters shut their shells and will not feed, but during ofl-shore winds 

 they fill up well. Though a hard winter leaves oysters in a weak condition, the losses on the beds by death are 

 greatest when the weather is changeable and high winds are frequent. 



A Baltimore correspondent writes : 



Thunder sours milk and kills oysters. Yon may load a vessel to its utmost capacity, start for market, and one good round clap of 

 thunder will kill every oyster in the vessel immediately. Pounding with an ax upon the derk of a vessel, when oysters are thereon, or 

 pounding upon the side of a vessel with a heavy weight, will kill every oyster that feels the jar. 



I am not sitre of the precise truth of this last assertion; but I know, that on the Massachusetts oyster-schooners 

 no wood-chopping is allowed, and I have heard it argued that steamers coitld never be used in transporting 

 Virginia oysters northward to the planting-beds, because of the jar of the machinery. How sensitive oysters are 

 to feeling, ai)pears from the fact, that they almost invariably close, the instant a boat comes near the bed. It has 

 been said that they see the shadow ; but to dispose of this, it is simjily necessary to remind the reader that oysters 

 have no eyes. It is by perceiving tlje.jar in the water that they are apprised of the approach of some body, and, 

 acting on instinctive presumption that it is an enemy, they droj) their visors. 



Description of the Florida bays and rekfs. — On the other hand, how oysters contribute to the 

 advancement of the world of humanity, apart from the nourishment which men and various animals derive from 

 their juicy bodies, is well illustrated on the western coast of Florida and elsewhere in the Gulf of Mexico. The 

 extent to which organic, living agents are adding to the coast-line of this portion of the United States is 

 remarkable, the more so as we hardly expect results so large and substantial from any means short of volcanic or 

 geologic methods. 



All along the western or gulf coast of Florida, particularly at its southein end, are great numbers of bars of 

 oysters, worthless (in their natural growth) for civilized humanity, but beloved of the raccoons, which nightly come 

 to eat them, and hence called "coon-oysters". Many of these reefs go bare at low tide, and you may walk about 

 on them. They consist of nothing but masses of oysters so crowded and compact, that a solid and level surface 

 (seamed by frequent shallow channels and spaces a few inches wide) covers over the wliole reef, which may be 



