ANATOMY OF THE EARTHWORM. 263 
DicEstive system.—Before proceeding any further in the 
description of the anatomy of the earthworm, it is necessary 
to explain the method which has been adopted in dissecting. 
The best way of killing the worm, which should be of as 
large a size as can be obtained, is with chloroform, though 
spirits of wine can be made to answer the same purpose. 
The advantage of chloroform is that it leaves the subject lax 
and pliable, whereas in spirits of wine rigidity often occurs, 
which renders careful dissection impossible. A pin being 
inserted in the first or labial segment, and the worm pinned 
firmly in a gutta-percha trough, the dissection may be 
commenced by a dorsal, lateral, or ventral incision, which 
should extend from the first to the thirtieth segment. This 
being done, the cut edges must be separated and pinned out, 
as much longitudinal tension being used as possible. The 
organs of the body will then present a very beautiful sight. 
Many, though, are concealed because of their transparency, 
and great difficulty will be found in manipulating certain 
organs on account of their tenuity aud the fluid nature of 
their contents. These difficulties will be entirely obviated by 
filling the trough with pure spirits of wine.* A most marvel- 
lous change then comes over the appearance of the extended 
annelid ; numerous little fibres display themselves, running 
from the pharynx to the transverse muscles, which also 
bece:ne more evident; the ciliated tubules in each segment 
make their appearance, and, what is most important, the 
reproductive organs become so hardened as to admit of 
careful dissection. I cannot but attribute some of the 
errors which have been made by the older and certain recent 
observers to the want of some such method of dissection as 
this. Fig 5 represents a worm opened by a dorsal incision, 
and treated in this way. 
Mouth.—The mouth in the earthworm is formed by the 
incomplete structure of the first segment of the body (fig 9). 
The incomplete ring is a conical or nipple-shaped projection, 
of a very fleshy, muscular nature, forming what may well be 
called an upper lip. The mucous membrane of the mouth is 
reflected inwards, and lines a large oral cavity, considered as 
the pharynx (fig. 5, 6, fig. 6). The mouth forms the subject 
of several figures and a good deal of letter-press in Morren’s 
memoir; but it appears to be a very simply formed orifice, 
* Mr. George Busk, who has for many years made the earthworm a 
favorite study, and who very kindly assisted me when first commencing its 
dissection, was, I believe, the first to use chloroform and spirits of wine in 
this way; [ regret very much not having had the benefit of his advice in 
preparing this paper. 
VOL. IVY.—NEW SER. ph 
