260 E. RAY LANKESTER, ON THE 
system, Circulatory and Respiratory systems, Nervous system, 
Secernary system, and Reproductive system. I may here 
mention that the majority of my observations have been made 
on the Lumbricus terrestris, though I have also dissected many 
individuals of L. agricola. 
TEGUMENTARY SYSTEM.—The tegumentary and muscular 
systems of the earthworm are so intimately united that it is 
somewhat difficult to describe the one apart from the other. 
If a vertical section be made of a portion of the integument 
of Lumbricus, three distinct strata or layers will be dis- 
tinguished. The external one is the epidermis, the middle 
the pigmentary layer, and the internal the muscular layer. 
If a very thin section of this description be made and 
placed beneath the microscope, the appearances drawn 
in Pl, VII, fig. 12, areseen. The epidermis (e) appears to be 
almost structureless and transparent, having, however, a cer- 
tain finely granular, striated aspect. The pigmentary layer 
(d) contains numerous dark-brown cells, irregularly disposed 
in a semi-transparent homogeneous matrix, in which also 
ramify very numerous blood-vessels. The disposition of these 
capillaries is towards the exterior, the larger branches from 
‘which they are derived being situated in and above the 
muscular layer. The muscular layer (c), which varies in 
size in various parts of the integument, is generally by 
far the thickest, composed of minute fibres, crossing and inter- 
crossing in various directions, the more superficial ones having 
a direction parallel with the longitudimal axis of the body, 
whilst the deep-seated fibres run exactly at right angles to 
these. Within the muscular {layer a small species of nema- 
toid (b) may be frequently detected. They are very abundant 
in all parts of the earthworm, but do not appear to do much 
harm. I shall have occasion hereafter to refer to this parasite 
(the Anguillula Lumbrici of Dujardin) in speaking of the 
generative organs, where its existence has given rise to many 
errors. A delicate layer of cells is perceptible beyond the 
muscular coat (a), which probably belong merely to the cor- 
pusculated perivisceral fluid. 
The tunic thus formed is constricted into various rings, or 
annulated, at short intervals throughout the length of the body, 
whichis of a cylindrical tapering form anteriorly, but broad and 
flat as the posterior region is approached, terminating at length 
very suddenly by a rapid diminution in the size of the annuli. 
If a worm be drawn through the hand, from head to tail, no 
perceptible impediment to its passage is felt; but if the 
reverse operation is tried and the worm be held by the 
