238 THE FISHERIES OF THE UNITED STATES. 



female oysters cmptj' tlieir generative products directly into the surrounding- water, whereby the likelibood of the 

 eggs meeting witli the male cells becomes diminished. What with falling into the mud and what with a lessened 

 chance of becoming impregnated, it is not unlikely that Miibius' estiuuite is very nearly correct; but tlie American 

 oyster, whose yield of eggs is much greater, not ouly on account of its larger size, but also because the eggs are 

 smaller than those of the European, has probably still fewer chances of survival.* The vigorous growth of small 

 organisms on surfaces fitted for the attachment of young oysters also tends to cause sediment to gatlier in such 

 places iu tlie interstices of the little organic forest, where the eggs of the oyster no doubt often become entombed or 

 smothered by the crowded growth surrounding tliem."t 



Interference of other animal life. — "We have called attention," continues IMr. Ryder, "to the probable 

 iuterfereuce of small organic growths to the fixation of the young fry; in practice it is found that the larger 

 organic growths which establish themselves on the collectors also become injurious. The two most conspicuous 

 types are the sessile ascidians or tunicates and the barnacles. I have frequently found fully one half of the surface 

 of a slate covered with a dense colony of ascidians ; iu this condition a great iiercentage of available surface is 

 lost which ought to serve for the attachment of spat. The surfaces so occupied would also be comparatively clean 

 were it not for these organisms, which actually become a serious annoyance. They, like the oyster, affix themselves 

 to the slates while still in the free swimming larval stage, since the surfaces designed for the oyster are equally 

 well adapted to them. The barnacles, which also afQx themselves in great numbers, become a nuisance for the same 

 reason The larval barnacle is an extremely active little creature, and dashes about in the water with great rapidity. 

 As soon as it has completed this stage of its growth, it betakes itself to some object, to the surface of which it 

 attaches itself by the head end, when a singular change takes place, at the end of which it is fouiul that it has 

 begun the construction of the curious conical shell which it inhabits. They grow very rapidly, so that iu a couple 

 of mouths the shell will already measure over half an inch in diameter. In this waj^ farther inroads are made ujion 

 the room which should be taken ui) by oysters. 



"Of course the larger types arejiot alone in taking up space, since infusoria, bryozoa, polyps, etc., are also 

 culpable, as well as algce, such as diatoms and the higher forms. The only remedy for this accumulation of animal 

 growths on the surfaces of the slates and other collecting apparatus, will be to have the frames which hold the slate 

 iu jjositiou so arranged that each tile, shingle, or slate can be removed, iu order that it may be leadily overhauled 

 and these organisuis removed from the surfaces which it is desired shall remain clean This work would have to be 

 done at intervals of every two or three weeks, and should be conducted with great care, so as not to remove the 

 oysters which have affixed themselves along with the other things which it is the intention to destroy. The removal 

 of the smaller forms from the surfaces of the slate would be more difficult, and attended with danger to the fry 

 already attached. With this object in view, I would suggest the use of wooden racks or frames lying horizontally, 

 which would receive the slates into deep notches made with a saw, so as to hold them vertically or edgewise, 

 rendering their removal, for the purposes of cleansing, and their replacement, an easy matter. Other devices would 

 no doubt answer the same purpose, and be more convenient even than the last. If posts were securely fixed in the 

 bottom eight or ten feet apart, so as to project a foot or so above the water at the highest tide, a single board six 

 inches wide, nailed against the tops of the posts edgewise, and extending from one to the other, would i)rovide a 

 simple arrangement from which to hang the slates singly, by means of galvanized wire fastened or hooked to nails 

 partly driven into the board. By the help of this plan one man with a boat could overhaul many hundreds of 

 slates in a single day, and effectually care for them for a whole season. This last contrivance would not answer 

 well, i)erhaps, where there was a swift current, but would be a most admirable arrangement in still ponds or "claires". 

 Iu such places the whole area might be provided with posts grouped or placed in rows, so that when the attendant 

 was at work he could pass in order from one row to the other in a narrow boat, or two attendants in one boat could 

 take care of two rows, the ones on either hand, at the same tinje.''t 



Food of the oyster. — "The food of this mollusk, as is well known, consists entirely of microscopic beings 

 and fragments of organic matter, which are carried by currents from the paljts and gills, which have been already 

 described, to the large mouth of the animal at the hinge-end of the shell. The inside of the gullet and stonmch, 

 like some other parts of the body, are covered with cilia, so that food once fairly in the mouth will be carried by 

 their action down to the cavity of the stomach, where it is carried into the folds and deep pouches in its walls, and 

 even into the openings of the bile ducts, to undergo digestion or solution, so as to be fitted iu its passage through 

 the intestine, to be taken into the circulation, and finally disposed of in building up the structures of the body. 



"Along with the food which is taken, a very large amount of indigestible dirt, or inorganic matter, is carried in, 

 which in a great measure fills up the intestine, together with the refuse or waste from the body. This material, 

 when examined, reveals the fact that the oyster subsists largely on diatoms, a low type of moving plants which 

 swim about iu the water, incased in minute sandstone cases, or boxes, of the most delicate beauty of workmanship. 



* According to estimates which I have made, based on the figures of the eggs of Ostrea edulis, given by M. Davaine, they are -j-Jn "f ^m 

 inch iu diameter. Estimates based ou the Cjjures of Lacaze Duthiers give y^tj of an inch, while Miibius estimates the size of the young 

 try at -ri?! of an inch. 



tOp. cit., pp. 4'J-50. 

 tOp.i-it., i>p. .'in, r,I, 52. 



