THE SHELLFISH INDUSTRY 313 



and are capable of almost unlimited expansion with the 

 certainty of producing great quantities of highly nutritious 

 food. 



It would obviously be of the greatest value if large 

 supplies of spat oysters could be produced under artificial 

 conditions for subsequent laying on the commercial beds. 

 To this end a series of experiments are being carried out 

 at Conway during the summer months. Adult oysters 

 are placed in the tanks under a series of different conditions 

 and the effect of various kinds of food on the production 

 of young and the settling of spat studied. So far, the 

 experiments have not been very conclusive but good results 

 have been obtained by placing large amounts of brown 

 seaweed in the tanks, these produce great numbers of minute 

 " spores " — or seeds — on which the young oysters readily 

 feed. Temperature has an important effect on the spawn- 

 ing of oysters, the higher the temperature the more frequent 

 the changes from male to female in the native oyster, 

 and so the more frequent the production of batches of eggs 

 which are incubated within the shell of the parent for some 

 days before they swim out into the sea. At first they are 

 whitish and the parent is said to be " white sick," but 

 later, when the young begin to feed, they turn darker and 

 form a greyish mass about the gills of the " black sick " 

 parent. The Portuguese oyster does not incubate its 

 young which develop from the earliest stages in the sea. 

 It has been suggested that they might be established in 

 this country by obtaining ripe adults, opening them and 

 scattering the reproductive products in the water over the 

 beds, where the young would, it is thought, settle and grow. 

 This process would have to be repeated each year because, 

 as we have seen, the water is here too cold for this oyster 

 to spawn naturally. 



