110 E. RAY LANKESTER, ON THE 
fluid, whilst this latter removes waste matters from and 
oxidizes the tissues, and performs all the offices of excretion 
and secretion. 
Nervous System.—The nervous system of the earthworm 
consists of a sub-intestinal and supra-intestinal chain of 
ganglia, with their branches. I have little or nothing here 
to add to the very elaborate, accurate, and detailed descrip- 
tion given by Mr. Lockhart Clarke, in his paper published 
in the ‘ Proceedings of the Royal Society’ for 1857, but 
will give a brief description of the subject of his researches, 
in which I shall make extensive use of his essay. 
In the centre of the third ring of the worm, overlying the 
pharynx, are two closely united pyriform ganglia, or a single 
bilobed ganglion, of which the lobes are united by their 
broad ends in the mesial line. This is the supra-wsophageal 
ganglion. The small end of each of its lobes divides into 
two nerve-trunks, of which one forms the root of its cephalic 
nerves (fig. 6), and the other the pharyngeal crus, which 
curves round the sides of the pharynx, to join the first sub- 
ventral ganglion. 
From each crus, or from either side of the collar thus 
.formed (see fig. 6), there spring eight or nine nervous 
branches. The first four or five arise from the under part of 
its anterior half, and immediately enter the upper surface of 
a minute and delicate cord-lhke chain of ganglia, the chain 
which was above designated the supra-intestinal portion of 
the nervous system. This very interesting structure was, 
to all imtents and purposes, discovered by Mr. Clarke, since 
Brandt and others had only spoken of it as a simple dorsal 
twig, given off from the bilobed cephalic ganglion. The 
chain lies on the side of the pharynx, concealed by the crus. 
The breadth of its first ganglionic enlargement is the =),th 
of an inch in a good-sized worm. Each border of the chain 
gives off several trunks of considerable size, which unite to 
form a continuous plexus, supplying with its inner part the 
muscular and mucous coats of the pharynx, with its outer 
the muscular bands and salivary tubules. From the pharynx 
the plexus descends along the side of the cesophagus, lying 
on the abdominal vessels, and communicates with minute 
filaments from the nerves of the subventral ganglia. 
The four or five nerves which are given off on either side 
from the posterior part of the crus communicate with each 
other by loops before they leave it. The first and largest 
sends some filaments to the muscular bands of the mouth, 
upon which they communicate by evident but shght dilata- 
tions with the plexus of the pharyngeal chain, and, after sup- 
