12 



REPORT ON OYSTER CULTURE 



In the British waters and those of France spatting usually takes 

 place when the parent oyster is from three to four years old, 

 although it is not uncommon to find oysters milchy at a much 

 earlier period. 



It has not been clearly ascertained how often during life breed- 

 ing takes place, but there is no reason to suppose that it does not 

 frequently occur in the lifetime of the same oyster, although it is 

 supposed that not more than 10 per cent, of the stock on any bed 

 will usually spat during any one season. 



As oysters, however, from various causes, have been known to 

 spat very late in the year, it is impossible with accuracy to state 

 the proportion of full-grown oysters that breed annually. 



The young oyster when perfectly mature rises immediately to 

 the surface upon its emission from the parent, after which it 

 adheres to the first clean hard substances it meets with; this 

 motion is effected by what has been termed a swimming pad {see 

 Figures 6, 7, 8, 9), but which is in truth but the protruded 



Fig. 6. 



Fig. 



Fig. 8. 



Fig. 9. 



lobes of the mantle and not an organ specially formed for loco- 

 motion, seeing that by it the shell is secreted. It is by this 

 organ also that the oyster attaches itself, and this too in the 

 same way that it forms its shell. Swimming with open shells and 

 extended mantle uppermost on meeting with a clean hard surface 

 it remains in close contact with it and secretes over that part of 

 the substance which it touches a coating of the same material of 

 which its shell is formed—the first coating is followed by other 

 layers — and so the once free oyster becomes fixed, and by a repe- 

 tition of the process from time to time the necessary increase of 



