ANATOMY OF THE EARTHWORM. 101 
adopting such names as “‘red”’ and “colourless,” or “vascular” 
and “ perivisceral,”’ fluids, to using the terms “‘ pseudo-hzmal ” 
or ‘‘ chylaqueous system.” 
Colourless or Perigastric Fluid.—On opening an earthworm 
by a longitudinal incision the various chambers of the body 
formed by the interseptal muscles will be found to contain a 
certain amount of a free fluid, having a more or less milky 
appearance, but generally very nearly clear. This is the 
“colourless ”’ or “ perigastric fluid;” it varies very considerably 
in amount in different specimens, but is always most abundant 
towards the posterior end of the body. Though the interseptal 
muscles or diaphragms divide the perivisceral cavity of the 
earthworm into various chambers, it must not be supposed 
that each of these is hermetically sealed. In addition to the 
general osmosis by which the fluids of two contingent chambers 
can be exchanged, there are openings in the diaphragms, 
imperfect attachments to the intestinal wall and ganglionic 
cord, by means of which a communication is established 
freely from one end of the body to the other. Thus it is that 
in the last segments of the body we find by far the largest 
amount of perigastric fluid, containing also a variety of con- 
spicuous foreign bodies, in the form of small white cysts, 
detached setz, &c; the fiuid itself also has a decidedly milky 
appearance. It was this congregation of foreign bodies at the 
posterior portion of the worm which led Sir Everard Home 
to regard the earthworm as self-impregnating and viviparous ; 
it is, no doubt, owing to the continual pressure in an antero- 
posterior direction, to which the movements of the worm 
subject its body, that this accumulation takes place; but it 
of course depends also on the fact that there is a free commu- 
nication between the various cavities, and that the fluid has 
no definite course of circulation to follow. In most cases, 
when a worm is opened, the anterior segments of the body 
will be simply moist, whilst the fluid increases in quantity as 
the posterior annuli are approached. 
Communications with the exterior.—The perigastric fluid 
has two direct and apparently special series of communications 
with the exterior, by means of which it can escape from the 
worm’s body; and another equally special series of communi- 
cations, by which it appears that fluids can pass from the 
exterior, and become part of its substance. The most impor- 
tant of the two series of exits is that furnished by the 
“seomental organs,” described in my last paper, which, by 
respiratory, and by others as nutrient; the truth being, probably, that its 
function combines, more or less, the offices of all three, or of the first two 
at least. 
