207 
not fit for marketable purposes until at least a year and a half 
or two years old, and consequently the total number of young 
removed, as estimated in my previous report, would he a total 
sacrifice. 
As will be seen by the table showing the number of oys- 
ters removed, this sacrifice probably amounted in 1878 to 
148,800,000 oysters. 
By reference to the tables showing the success or failure of 
the several spatting seasons, it will be seen that there is little 
or no regularity of either success or failure. 
We have only been able to investigate the spatting of three 
seasons, and it may be found by subsequent observations that 
two similar seasons of success, moderate success or failure wfill 
follow each other, but so far this has not been the case, and 
in the period of three years we have, comparatively to the 
other seasons, one at least of successful attachment. 
I can see no reason for supposing that there is any regular 
recurrence of the spatting seasons, but am inclined to believe 
that the success or failure is due to two causes; variations of 
temperature and variations of density. 
I have no means of ascertaining either the changes of tem- 
perature or density in the years preceding those in which I 
have been engaged upon this investigation, and in both seasons 
I arrived in the Sounds too late for the temperatures or deter- 
minations of density obtained by the party to be of practical 
value. 
Oysters will and do live in very dissimilar temperatures, and 
in waters of very different densities, as is shown by their ex- 
istence in the waters of North America from Nova Scotia to 
the Gulf, and on both Atlantic and Pacific Coasts. That the 
mature oyster is a hardy animal, readily adapting itself to 
mew conditions and environment, is shown by the ease with 
which it is transplanted from the warm waters of the Ches- 
apeake to the colder ones of New England; from the dense 
and salt waters of the ocean and Bay, to the brackish waters 
of the creeks and rivers or vice-versa, and from soft bottoms 
to hard or the reverse, but naturally this hardiness is not a 
quality of the immature oysters or the swimming embryos. 
