256 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



millimetre long. In older specimens the fibrous portion 

 of tbe brain becomes proportionately larger and mor* 

 complex, and the neuroglia is better developed. Tie 

 nerve cells also become aggregated into groups, separated 

 by bands of fibrous tissue. 



The (Esophageal 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 chsetigerous 

 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, 

 (3) 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 Yentral 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 chaetigerous 

 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 



