104 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



water may flow readily in between and around them. 

 The cases of collectors I measured were about 6 feet in 

 length by 2 feet in breadth and 3 feet in height ; each holds 

 120 tiles arranged in 10 tiers or layers. The tiles in any 

 tier are placed with their long axes at right angles to those 

 of the tiers above and below, as is shown in PI. L, fig. 2. 

 This it is thought breaks up better than any other 

 arrangement the currents of water as the tide runs through 

 the "ruche" and so gives the young oysters a better 

 opportunity of affixing themselves to the tiles. This is 

 the arrangement in the " gabaret " collectors or " tuilles 

 en ruche," which is considered after numerous experiments 

 to be the best form at Arcachon, but various other forms 

 of tile collectors are in use elsewhere and are better suited 

 to special local conditions, such as depth of water and 

 softness of bottom. The tiles are always placed with the 

 convex surface upwards as it is very important that there 

 should be as little opportunity as possible given for the 

 collection of any fine sediment in which the young oysters 

 might be smothered. 



I was very fortunate in seeing some of the tiles just 

 after the young oyster spat had been deposited, and one 

 of the figures (PI. I, fig. 3) represents Mons. Dubourdieu 

 holding up such a tile, covered thickly with the little 

 amber coloured specks, less than T X g- inch across, for me to 

 photograph. There may be several hundred such young 

 oysters on one side of a tile. I had the advantage of going 

 round with Mons. Peseux and Mons. Dubourdieu on July 

 3rd, when they were inspecting their collectors, and they 

 and also Mons. Daste assured me that this was an especi- 

 ally good year for spat. They attributed that to the con- 

 tinued fine weather and especially to the high temperature 

 of the water. 



During my stay at Arcachon the water in the "bassin" 



