INTRODUCTION. 
XVll 
the shell of a crab, or a limpet, from which the entire flesh 
has been removed and replaced by a tenacious glaire. No 
doubt the fii-st part of the process consists largely of ma- 
ceration, and continued pressime, by means of which the 
juices of the food are extracted. 
The nutritive matters thus obtained are then subjected 
to the action of the bile. No anatomist, I believe, has as 
yet attributed a liver to these animals, but I have little 
doubt that such is the character of a structure which I am 
about to describe. In dianthus, crassicornis, Peachia undata, 
and others, the stomach-wall is lined on the interior side of 
its upper portion (the side, I mean, which is within the 
interseptal chambers) with a thick highly-coloured sub- 
stance. In the first two named this is yellow or orange, in 
the last salmon-red. This lining is {dianthus) about half a 
line in thickness, of a pulpy tissue, an-anged in irregular 
lobules, covered with a ciliated epithelium (Plate XI, fig. 
1, d). On being crushed down, the pulp is found to be 
composed of a nearly uniform mass of yellow fat-cells, the 
largest of which are about *0003 inch in diameter, and the 
smallest immeasurable points. Cnidie occur numerously in 
the true stomach-wall, but none in this lining-coat. I am 
justified, then, in presuming this organ, from its colour, 
form, position, and structure, to be a liver* 
In Aiptasia I find what I think an analogous structure, 
but with a slightly varied position. The septa, instead of 
being inserted into the stomach-wall from the point where 
they spring off to the summit, recede from it at their u])per 
part, where their edges carry rounded pulpy lobes, which 
under pressure consist of a clear tenacious sarcode, carrying 
a moderate number of brown pigment-cells. The sarcode 
is composed of globose cells, averaging *0005 inch in 
diameter, each containing more or fewer oil-globules, 
• As an example of the need of caution in such observations as these, 
I may be pardoned for mentioning the following circumstance : — While 
viewing the surface of the pulpy tissue above described under a good 
reflected light with a power of 133 diameters, I saw it forming irregular 
lobes, with deep narrijw sinuous depressions. Over the surface, and 
chiefly following the lines of the sinuosities, I noticed meandering white 
lines, like veiy slender branching threads. The thought that I had dis- 
covered veritable nerves immediately occurred to me ; but turning the 
mirror of the microscope to test the observation with a diflerent .angle of 
the light, I found I had been looking at merely the lUjht rcllected from the 
ed^e of the smooth lobules / 
