200 PHOLADID #. 
hour’s constant observation under the lens, issued from the 
anal siphon, a sufficient proof of the non-communication of 
the two; but as soon as the anal siphon was allowed to reach 
the water and obtain a supply, the current recommenced. 
I now come to another experiment from which Messrs. 
Alder and Hancock conclusively infer the connection of the 
siphonal currents. They state, “that the nosle of a blowpipe 
charged with a coloured fluid was placed at the mhalant orifice 
of a Pholas, and immediately a quantity was drawn into the 
animal. Watching carefully the result, we had soon the 
satisfaction of beholding a blue-stamed stream issue from the 
exhalant orifice.” 
To this I observe, that having tried the experiment again 
and again, failure always occurred; as the animal, after re- 
ceiving the coloured fluid, which was applied without difficulty, 
in general immediately discharged it by the pedal gape, or by 
the branchial aperture overwhelming with coloured matter 
both tubes, the orifices of which, from their inflection by the 
animal, were so retracted and blended together as to be undis- 
coverable ; of course, any issue of liquid from a particular tube 
was undistinguishable. When, in any example, the fluid, 
which was coloured by archil, remained a little time without 
expulsion, I opened the branchial cavity to see if the gill- 
lamin and interbranchial tubes showed any increased infla- 
tion or colour from the filtration of the mjection, but no 
unusual appearance presented itself. I also opened the anal 
vault and collected with a camel’s-hair brush as much of the 
moisture as possible ; this was applied to a very small quantity 
of distilled water, but no trace of colour appeared; we may 
then presume that none of the injection had passed from one 
siphon to the other. But when the coloured fluid was ad- 
ministered anally, all the interbranchial tubes were at once 
filled and remained inflated more than an hour, representing 
minute well-filled hoses, which bore the pressure of a delicate 
wooden stylet, and exhibited the fluctuations of the liquid, 
which, on its removal, instantly reverted to the points of dis- 
placement, without any escape into the branchial chamber. 
We may therefore conclude, that the interbranchial tubes are 
