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LumlDricus agricola. 
In Lumbricus, the dotted substance of the central nervous system 
represents a more developed state than it does in Nereis, it having a 
much more comphcated structure ; this is at once prominently apparent 
in transverse and longitudinal sections. The substance consists of 
tubes, and exhibits in sections a minute reticular appearance, the 
tubes being generally very slender; they vary a great deal as to 
their diameter, some are extremely slender, others are thicker but 
their average size is small. The tubes have, in the ventral nerve- 
cord, a longitudinal course, principally as may be seen in longitudinal 
sections. Between the longitudinal tubes, slender tubes are, however, 
interwoven, running in all directions, and forming a complicated web 
or plaiting. This plaiting is present to a much greater extent than 
is the case in Nereis, and at the same time the diameters of the 
tubes are generally much smaller than they are there. 
As is well known there are no ganglia in the ventral nerve-cord 
of Lumbricus, and thus the dotted substance is uniformly extended 
along the whole nerve-cord. 
The fibrillæ described by many previous authors, e. g. Clapa- 
RÉDE, are, in my opinion, as before mentioned, only the transsected 
sheaths of the tubes which are the real constituents of the dotted 
substance. 
In respect of the origin of these tubes forming the constituents 
of the dotted substance, it may be said so far as my experience 
goes, that their origin is quite similar to what is found in Nereis 
and Homarus. 
As to the nervous processes of the ganglion cells, I have ob- 
served the same two types as are described in Homarus, viz. 
i) nervous processes retaining their individuality and directly becom- 
ing nerve-tubes (either of a peripheral nerve or running longitudinally 
in the ventral nerve-cord [fig. 84]) but which give ofif side-branchlets 
to the dotted substance (fig. 71, /, g), and 2) nervous processes which 
lose their individuality and are, by subdivisions, entirely broken up 
into slender tubes losing themselves in the dotted substance 
(fig. Ji, a, cl, h and fig. 72). 
As to the course of the longitudinal nerve-tubes of the dotted 
substance, and the double origin of the peripheral nerve-tubes, I have 
observed conditions very similar to those stated of Homarus, but 
my observations have been rather imperfect, as I have not obtained 
such staining in Lumbricus as I have in Homarus. 
