152 BRODE. [VoL. XIV. 
so situated in D. vaga. He does not figure the nerves from 
the commissure corresponding to those found by Reighard. 
He found that as many as three nerves were given off from the 
ventral cord in a segment. These correspond in position to 
some of the nerves found in D. vaga. 
(b) Descriptive. 
The nervous system of Devo vaga consists of a central 
ganglionated cord with lateral nerves and a sympathetic system 
which covers the pharynx. 
Central Nervous System.— The central cord is made up of a 
dorsal ganglion, the so-called “ brain,” and an indefinite number 
of ventral ganglia, corresponding in number to the segments of 
the body. The dorsal ganglion is united with the first ventral 
ganglion by a commissure, which passes around the alimentary 
canal. The dorsal ganglion (Pl. XIII, Figs. 3, 6, dg.) is situated 
in the first segment (preoral lobe) and consists of two pear- 
shaped masses united at their larger ends, while the smaller 
ends are drawn out to form the commissures. The ventral 
ganglia in the first four setigerous segments are crowded 
together so that no space is left between them. However, 
the characteristic lobed appearance clearly shown in the follow- 
ing ganglia may also be traced in this part of the cord. The 
ventral cord consists of two large bundles of fibres on which 
are found at intervals of one segment the masses of ganglion 
cells which form the ganglia. An intermediary nerve is also 
clearly visible. 
The typical ganglion (Pl. XIII, Figs. 6, 8) consists of a series 
of four distinct enlargements. The second is the largest and 
is near the middle of the ganglion. The entire mass, with the 
exception of the posterior enlargement, lies in one segment and 
occupies a position a little posterior to the middle. The poste- 
rior enlargement occupies a position close to the dissepiment, 
and apparently has been pushed back so as to lie in the next 
segment. 
At the tail end of the worm or at a fission zone, the ventral 
cord is in connection with the epidermis (Pl. XIII, Fig. 7), from 
