156 BRODE. [VoL. XIV. 
s.g.), which are situated on the sides of the pharynx at the junc- 
tion of the anterior with the posterior region. The connecting 
nerves are distributed over the dorsal part of the pharynx, the 
whole system lying just beneath the epithelium of the canal. 
The main trunks (s.z.) are given off from the inner sides of 
the oesophageal commissure and from points a little below the 
brain. Their course is slightly dorso-lateral until they reach 
the pharynx, where they divide into two branches; the larger 
(m.s.n.) takes the position in the groove above alluded to, and 
the smaller extends upwards and back over the side of the 
pharynx and unites with the larger branch at the ganglion. 
At the place of branching, a large commissural nerve joins 
the two main trunks. A large nerve also extends over the 
dorsal side of the pharynx, uniting the two ganglia. Between 
these two commissures there are about fifteen smaller nerves, 
which also extend over the pharynx, anastomosing with the 
upper longitudinal trunks. 
The ganglia (s.g.), two in number, are double, the ganglionic 
mass being divided into an anterior and a posterior half. These 
parts are elongated dorso-ventrally, and the anterior mass is 
smaller than the posterior. 
Sensory cells are found in the pharyngeal epithelium, which 
in some cases are apparently connected with the branches of 
the sympathetic nerve. These cells are especially numerous 
along the two main nerve trunks. 
No connection has been found to exist between the sympa- 
thetic system and the nerves from the ventral cord, and no 
indication of a sympathetic nerve in Leydig’s sense has been 
observed. 
(d) Comparative. 
The nervous system in all Oligochaetes consists of a dorsal 
ganglion lying above the alimentary canal, and a ventral 
ganglionated cord connected with it by a circum-oesophageal 
commissure. 
The dorsal ganglion may be found in the first segment or it 
may be pushed back to lie in the third segment. In the devel- 
opment of the earthworm the brain is formed in the first 
