OYSTER CULTURE IN HOLLAND. 701 



ing to the above requirements are found on the spots I will 

 indicate on the map. 



In order now further to bring before your mind how 

 the value of one locality above another for this and other 

 purposes of oyster-culture, appears to be gradually estab- 

 lished by experience, and is, indeed, recognized by those 

 interested in this industry, I have promised to give you a 

 few comparative numbers of the sums for which the same 

 plots were leased in 1870, and will be so from 1885 

 forwards :- 



Allotment No. 162, size 12 acres, was leased 



In 1870 for is. 8d. a year; will be in 1885 ^"202 a year. 

 No. 163 12 ac. ,, is. 8d. ,, ^"227 



164 12 135. 4d. ^252 



176 12,, ,,,22ios. od. ^508 



220 120 ,, ,,^25 i8s. od.. ^33 155. ,, 



,,.138 12,, ,,^i8ios. od. ^762105.,, 



Others have gradually come down in the market, as for 

 example- 

 No. 280 24 acres brought in 1877, ^45 i6s. ; in 1879, l IOs - 

 ,, 415 18 ,, ,, 2 is.; in 18^2, lod. 



The fluctuation is, as you see, indeed considerable, and 

 only rivalled by that mysterious fluctuation of spat, which, 

 in the breeding season, is carried to and fro at each turn- 

 ing tide, all through the basin of the eastern Schelde. 



A question which we were also eager to answer in 

 continuing our investigations at the Zoological Station, was 

 this : From whence is the spat that occurs in such myriads 

 on the Schelde essentially derived ? The interest of this 

 question was increased by the fact, that among the oysters 

 which were dredged on the cultivated beds, the number of 

 ripe specimens carrying eggs was very rare. This was 

 partially explained by the fact, that the oysters are gener- 



