700 OYSTERS, AND ALL ABOUT THEM. 



will not then fix upon them ; if brought out too late the 

 spat may have altogether disappeared for that season. It 

 is thus a very important question when and where to deposit 

 the collecting tiles. Up to the present, oyster-culturists 

 have been guided mostly by empirical notions, tradition 

 and experience having decided what portions of the sea 

 bottom were most fertile for the collecting of the young. 

 Theoretically this question is dependent on circumstances 

 which are, indeed, complicated. It must first be .asked, 

 where are the oysters that furnish the spat ? secondly, how 

 long does this spat swim about independently, before fixing 

 itself ? thirdly, what is the influence of the currents in the 

 vicinity of the' mother oysters upon the distribution of the 

 spat over a certain area ? 



It has been the object of a series of investigations 

 planned by the direction of the Dutch Zoological Station, 

 of which I am a member, to try and get definite and reliable 

 facts concerning these movements of the spat. I am sorry 

 to say, that in this respect our results up to the present 

 moment are rather scanty, although we are continuing 

 our exertions. One fact is generally accepted, viz., that 

 exceptionally good localities for spat collecting are those 

 where there is a strong current of fresh sea-water at each 

 tide in the immediate vicinity, and where, at the same time, 

 this current is broken by headlands or other causes, so as 

 to produce counter-currents of much reduced intensity. 

 The spots where these counter-currents occur are very 

 much valued, as are also those deeper pits here and there 

 found in the sea-bottom, above which a sort of whirlpool 

 is apt to occur. It would seem that in both these cases 

 the spat is more easily deposited, is, so to say, precipitated, 

 on the collecting-tiles or other substances (shells of dead 

 molluscs, &c.) to which it can adhere. Localities answer- 



