OF THE GULF OF MAXAAR, 
95 
that has idiosyncrasies to be separately observed, and I see 
from my notes taken on the spot that my observations of 
the pearl oyster were as follows : — 
Having desired that some live pearl oysters might be 
procured for me for the purpose, and some being brought 
to me accordingly after dark, I remembered that they are 
said to be most active at nighty and, putting them into 
a thin blown-glass soda-water tumbler full of sea water, 
brought a bright reflector and another kerosene lamp close 
to it on the table, so that I might get an excellent light, and 
with a good hand magnifying glass settled down to prefer 
their evolutions to dining, which I did closely for two hours, 
till the eyes, &c., ached beyond further endurance. 
One young pearl oyster, measuring by compass {|ths 
or, say, -||-nds of an inch from hinge line to contour dia- 
gonally, and having two others of nearly its own size 
attached to its shell by their byssi, walked up the smooth 
side of the glass 4 inches in 8 or 9 minutes. I could not 
time with closer exactitude, because I did not like to take 
my eyes off the oyster to look at my watch, lest on arriving 
at the surface the animal should throw out a byssal thread, 
and I should miss seeing it done. Thus the rate of progres- 
sion, though perpendicular, though on a smooth glass surface, 
and though the animal was weighted with two other oysters, 
making an addition of more than one-and-a-half times its 
own weight, was at about the rate of an inch in two minutes. 
Another osyter measuring -pj-ths of an inch across, which I 
timed exactly, maintained the same speed, covering 3 per- 
pendicular inches by compass in 6 minutes. 
The water in which the young oysters were brought me 
being somewhat turbid, I supplied them with water fresh 
from the sea, which was so clear that one could distinctly 
see living diatoniacice in it, and what seemed to be rotiferce, but 
were probably pearl oyster larrce, as well as a minute trans- 
