176 
millimetre long. In older specimens the fibrous portion 
of the brain becomes proportionately larger and more 
complex, and the neuroglia is better developed. The 
nerve cells also become aggregated into groups, separated 
by bands of fibrous tissue. 
The (sophageal Connectives arise from the anterior 
lobes of the brain. They run beneath the epidermis and 
circular muscles passing round the sides of the pharynx, 
and uniting about the middle of the third chetigerous 
annulus. The course of the connectives is marked 
externally by the metastomial grooves (figs. 2, 6). The 
connective of each side gives off (1) a nerve to each of the 
first two inter-annular grooves, (2) a nerve to the otocyst, 
(5) a nerve to the buccal mass which is probably connected 
with the stomato-gastric system, (4) numerous nerves to 
the epidermis of the peristomium and following segment. 
Each connective is a stout fibrous cord, with numerous 
cells upon its outer face. At the point of origin of the 
nerve to the otocyst, and along the course of this nerve, 
there is a considerable number of ganglion cells 
(fig. 49). The connective is enclosed in a sheath of neuri- 
lemma, which is better developed in old specimens, and 
by ingrowths partially sub-divides the fibrous part of the 
connective into two or three. 
The Ventral Nerve Cord is usually separated from 
the epidermis by the layer of circular muscles, but in some 
specimens the cord in the tail and in the last chetigerous 
segment, lies only just below the epidermis. — Its blood 
supply is derived from the two lateral neural vessels, 
which are connected with a series of capillaries lying 
chiefly on the dorsal face of the cord (fig. 24). 
The cord is non-ganglionated, ganglion cells occur 
moderately evenly distributed along the whole length of 
the ventral and lateral surfaces of the cord except at the 
