209 
Probably the influence of changes of environment, espe» 
cially of density and temperature of the water, is most se- 
verely felt by the embryos when in their free swimming state, 
and, in connection with the want of success of the spatting 
seasons in the Sounds, it is noticed that the temperature curves 
show a maximum change about the time when it is supposed 
that the young would attach in largest numbers, or about 
the period when they were swimming about in the water. 
It is also worthy of notice that Prof. Brooks, about this 
time, met with the maximum amount of success in his efforts 
to artificially raise the embryos. 
In consideration of the foregoing, I am of the opinion that 
the success or failure of any spatting season is dependent upon 
the equability of the temperature, and that the higher the 
temperature during the spring months the earlier the advent 
of the spawning season, and that an increased temperature 
will also hasten the development of the spat, and of the young 
oysters after they have become attached. 
I also infer that sudden and extensive changes of density 
will likewise affect the advent, duration and success of the 
spawning, though to a less extent. 
Subsequent to the attachment of the animal, changes of the 
conditions surrounding it are not of so much importance, 
though naturally such changes will more severely affect the 
delicate organism of the young oyster than that of the older 
and more hardened adult. 
During the first six months of its existence the oyster is ex- 
posed to the greatest danger from the numerous enemies 
which surround it. The thin, delicate shells, from one-six- 
teenth of an inch to one inch in diameter, are readily bored 
by the drills or torn off by the crabs, and the immense num- 
bers of both of these leave no room to doubt their destruc- 
tive effects. The inspection of the spat collectors in the Big 
Annemessex Diver shows that during the early months of 
their existence about 50 per cent, of the young oysters are de- 
stroyed, and future inspections of the hurdle will, I hope, give 
the rate of decrease in other periods of time. 
Naturally, as the animal progresses, it becomes more hardy 
14 
