1206 OYSTERS, AND ALL ABOUT THEM. 



tion of spat which is exuded in an immature state, and 

 floats about on the surface of the water at times in greenish 

 mucous masses. This is white-sick spat, which has escaped 

 before its time, owing to the inability of the parent to 

 contain it. This is apparently an unnatural occurrence 

 arising probably from a change of condition or a change 

 of temperature. This kind of spat forms a considerable 

 portion of the whole ; it is possible that a very small 

 portion of it may ultimately become sufficiently mature for 

 attachment, if not carried away or devoured by fish, but the 

 proportion of immature spat that ultimately attains maturity 

 is so small that it may be practically ignored. 



The parent oyster goes on producing and hatching its 

 ova for some time, as these may be seen oozing for several 

 days from the same oyster. In fact, from the time the ova 

 are first produced to the time the last germ of black spat 

 is emitted, a period of from three to six weeks probably 

 elapses, the process being accelerated by a continuance of 

 warm weather. 



The age at which reproduction commences has never 

 been exactly ascertained ; it is supposed, as a general rule, 

 to be from three to six years or more, though instances are 

 known of oysters being in a " milky ' state at a much 

 earlier stage. Mr. Frederick Wiseman has stated that he 

 has known an oyster white-sick when only a year old, but 

 it is highly improbable that the ova produced from a year 

 or two-year old oyster would ever come to maturity. 



It is believed by some that oysters do not breed every 

 year. Mr. Buckland held the opinion at one time that, like 

 salmon, they breed in a cycle of three, five, or six years. 

 The Irish Commissioners in 1870 formed an opinion that 

 they bred only once in ten years, but this was based upon 

 the examination of a bed during the breeding time, when 



