58 



THE EARTH-WORM 



C. The Nervous System. 



Cut through the anterior end of the oesophagus and carefully remove the 

 whole alimentary canal posterior to this. Push the pharynx over to one side 

 so as to expose the nervous system. 



The " brain " is situated on the anterior part of the pharynx in the second 

 segment of the body, and consists of a pair of supra-pharyngeal ganglia. Each 

 ganglion gives off nerves to the prestomium. These ganglia are connected (by 



-Spermatheca 



Anterior sperm 

 reservoir 



Posterior sperm, 

 reservoir 



Fig. 20. — A. Alimentary and Vascular Systems of Earth-worm (Lumbricvs) ; B. Nervous 



and Reproductive Systems. 



a pair of circum-pharyngeal commissures passing round each side of the pharjTix) 

 with a pair of sub-pharyngeal ganglia lying in the 4th segment. From them 

 the ventral nerve cord is continued straight back in the middle line to the 

 posterior end of the body. The ventral nerve cord is double, but the cords are 

 more or less fused together. In each segment the cord swells to form a gangUon, 

 which gives oU three pairs of nerves, one pair near the anterior septum and two 

 pairs near the posterior septum. 



D. The Reproductive System. 



The Earth-worm is hermaphrodite. The reproductive organs and ducts are 

 situated in segments 9 to 15. 



The ovaries are a pair of small pear-shaped bodies lying in the 18th 

 segment, one on either side of the nerve cord. Each is attached to the 

 posterior face of the septum between the 12th and 13th segments. Facing 

 the ovaries, in the same segment but on the septum behind, there are 

 two wide ciliated funnels ; these are the internal ccelomic openings of the 

 oviducts. Each oviduct passes through the septum between the 13th and 



