210 
and better able to resist the attacks of enemies and changes 
of environment, and thus we find on the unworked beds, 
where the oysters are practically in a natural state, that the 
decrease in passing from young growth to mature oysters is 
about 30 per cent., or about one- third of a given number per- 
ish in passing from the first to the fourth year of their exist- 
ence. 
Here our information ceases, but enough has been gathered 
to indicate the proportion which nature has assigned as neces- 
sary between the young and the mature oysters. For every 
1000 of the latter there should be 1500 of the former, if the 
number of brood oysters necessary to maintain the fecundity 
of the beds is to be kept up, and though this proportion is 
based upon data which is not quite sufficient, yet, as I have 
said, it is all that has been afforded as yet, and may be ac- 
cepted within certain limits. Certainly whatever it should 
be, the number of the rising generation of the animals should 
never be less than that of the older, or there should always 
be as many young as mature on any bed. 
A greatly increased proportion of young to mature oysters 
would show either one of the two tnings — either the mortality 
in passing from youth to maturity was much greater than 
shown by the dredging results in the Bay, or that a very large 
number of mature oysters had been removed by other than 
natural causes. 
In considering these several beds the question of food and 
other necessary supplies has not been considered, as it is evi- 
dent that when an oyster bed is formed and exists naturally, 
all the conditions for its successful life are probably present, 
and any failure of an important supply would be followed by 
a speedy extinction of all the oysters on the bed. Such deter- 
minations of the quality and quantity of the food, character 
of bottom and water, and other matters, are only of interest 
and desirable for the purpose of comparing one locality with 
another. Such was not the purpose of this investigation, and 
consequently the determination of those points has been but 
incidental to the work. 
Probably the fecundity of a bed is increased to a certain 
