382 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
No restriction was imposed. The rental of the property was to be paid yearly, 
and in 1877 the beginning was made of a fifteen years’ lease, with the option of giving- 
up the lease at stated times. The second re-rental of the property, however, was 
arranged to take place several years before the expiration of the lease, and was to 
allow a term of thirty years, with option of giving it up every five years.* * * § The present 
experience in the renting of the returned parcels, as explained to the writer by Mr. C. J. 
Bottemanne, inspector- general of the Holland fisheries, indicates that a shorter term of 
lease will in the main prove more satisfactory to the government as well as to the 
tenant, the government getting a fairer proportional rental, the tenants being more 
apt to have a better opportunity of obtaining favorable concessions. A yearly lease 
of all state cultural property is now to be inaugurated, with a right to have this 
twice renewed.! 
The actual oyster-grounds of Holland may be grouped as those of the Zuyder Zee 
and those of the Schelde estuary. The former, in spite of all efforts at their regener- 
ation, have remained profitless, and the lack of success in these measures is attributed 
partly to unfavorable conditions of a northern locality and partly to variation in water 
densities.! 
The Zeeland grounds, those of the Schelde estuary, became from the first the seat 
of the oyster industry. In the east arm of the Schelde the most fayorable conditions 
exist for growth and production; and here, in fact, is the only point in Holland where 
the artificial collecting of seed oysters has been profitably carried on. This region has 
proved a favorable one in the firm unshifting character of foreshore and even of deeper 
areas, and in the degree of salinity of its waters. The densities, it may be noted, 
varied between Goes and Bergen op-Zoom at different tides (July 16 to 20, 1892) 
between 1.023 and 1.015 (62° to 09° F.), conditions that appear to correspond very 
closely to those of regions of production in Frauce (Auray or Arcachon), although in 
the latter instances the water temperature at a corresponding season the year before 
was warmer by 5° to 10° F. 
It is in the East Schelde that the biological problems connected with the oyster 
have been studied — from the time, in fact (1870), when a critical investigation of these 
matters became necessary. To carry on observations as near as possible to the seat 
of the oysters spawning, the Dutch Zoological Society made use of a portable labora- 
tory, and under the auspices of this society were prepared the classic memoirs of 
Hoek, Hubrecht, and Horst.§ The embryology of the European oyster was here given 
its most careful study. Experiments were made upon the collecting of seed oysters 
in small closed ponds in which the water was aerated artificially, and the questions 
relating to the spawning of oysters in captivity were investigated, since in all experi- 
ments the impracticability of fertilizing the eggs of the European oyster proved a very 
serious difficulty. 
Certain problems connected with the East Schelde seemed also especially to 
require solution, such as those of the movement, duration, and distribution of oyster 
*Hubrecht, Int. Fisheries Exhibit (London), pamphlet, Oyster-Culture in Holland, 1883. 
t See pp. 387 and 388. 
t Dr. Hoek, in conversation with the writer, at the Helder, July 18, 1892, commenting upon the 
failure of recent experiments in the Zuyder Zee. 
§ Rapport sur les recherches concernant l’huitre et T ostreiculture, Leide, Brill, 1883-84. 
