OYSTERS AND METHODS OF OYSTER-CULTURE. 327 



labor to be expended in making the necessary excavations will be prouortionally 

 diminished, and no assistance from a skilled engineer will be required. 



Whether the si^awuing pond is excavated or not, the principle upon which the 

 system is constructed and operated remains the same, namely, that the area of the 

 canal systems and the ponds be about the same. In order that the fry be not car- 

 ried past the collectors, the area of the pond should not much exceed the total area 

 of the caiuils. lu order that the fry may be wafted to the outermost collectors, the 

 area of the canal system ought not to greatly exceed that of the poud or ponds. 



Canals constructed between a series of spawning ponds may also bo utilized; in 

 fact, a great many other modifications of the system are available, which would 

 become apparent only after a study of a given location. The plans for carrying out 

 this system would, in fact, have to conform to the demands of the location, so that it 

 may be said that each establishment would have to be designed in conformity with 



local conditions. 



**#### jf 



If cultch in the form of shells is the best (for which conclusion we have assigned 

 reasons), it follows that such material should be so utilized as to obtain the largest 

 possible return for the least jiossible outlay. In other words, if shell cultch is to be 

 used at all, let it be expeditiously and economically, and not wastefully and 

 unscientifically, employed. It has been found that even the sowing of shells is 

 profitable, as has been conclusively demonstrated, and in one type of culture, 

 namely, that which is practiced in deep water, it is probable that it is the only 

 practicable method which will be devised for a long time to come. While it is to a 

 great extent wasteful and at times uncertain, for the present, at least, there seems 

 to be no other which can be so economically and successfully operated over large, 

 open, navigable areas. Large areas operated by one individual or corporation can 

 not always be commanded, or only exceptionally, under the existing laws of the 

 States of Maryland and Virginia. In those States, however, where it is possible to 

 command the right to natural areas of water which are more or less nearly land- 

 locked, the system of merely sowing shells would be positively wasteful and not in 

 conformity with the results attainable under the guidance of the proper knowledge. 



It is found in the practice of shell sowing that extensive areas will sometimes fail 

 to produce any spat. This is apparently due to the presence of currents which have 

 swept the fry off the beds, or to the presence of sediment, which has put an end to 

 the first stages of its fixed career. Even after the spat is caught, great destruction 

 may occur through the inroads of starfishes, or a too rapid multiplication of worm 

 tubes over the cultch and spat. The latter is sometimes smothered in vast numbers 

 from the last-mentioned cause, as has been recently discovered by Mr. Eowe. Such 

 casualties are rendered either impossible or readily observable during their early 

 stages by the method of inclosing the cultch in suspended receptacles, as suggested 

 In thisjiaper. The netting will effectually protect the young spat against the attacks 

 of large starfishes, and no growth of barnacles or tunicates, worm tubes or sponges, 

 would be rapid enough during the spatting period, jiulging from an experience 

 extending through several seasons, to seriously impair the spatting capacity of the 

 cultch used in the suspended receptacles. Any of the larger carnivorous mollusks, 

 fishes, or crnstaceaus which could prey on the young oysters can also be barred out 

 and kept from committing serious depredations by means of the netting around the 

 cultch, as well as by means of screens placed at the mouth of the canal. 



The maximum efiicieucy of the cultch is not realized in any of the old forms of 

 collectors, for the reason that the cultch cannot be kept clean; secondly, because 

 both sides of the cultch can not be exposed to the passing fry ; thirdly, because the 

 fry can not be compelled to pass over and amongst the cultch repeatedly; fourthly, 

 because the cultch is scattered over too great an area and throughout only two 

 dimensions of a Viody of water, namely, its horizontal extent, where it is possible, as 

 I have Bhowu above, to do all this and more — that is, to avail ourselves of the possi- 



