NEEVOUS SYSTEM. 51 



the ventral body-wall, about midway between the 

 testes and the vesicles of the nephridia. 



In front of the first pair of testes they continue 

 their course through the seventh somite, and in 

 the sixth enter the epididymes. 



d. The epididymes are a pair of convoluted tubular 



bodies with thick white walls, lying in the sixth 

 somite. They secrete a substance by which the 

 spermatozoa are aggregated into spermaphores. 

 Prom the inner side of each a short duct leads 

 to the base of the penis, the duct of the right side 

 passing under the nerve-chain. 



e. The penis is a pyriform body lying in the sixth 



somite. It is wide at its base, narrow and tubular 

 in its distal part, and can be protruded some dis- 

 tance through the male genital aperture in the 

 second annulus of this somite. 



2. The female organs lie entirely in the seventh somite. 



a. The ovaries are a pair of minute filamentous bodies 



enclosed in small spherical sacs, lying close to 

 the mid-ventral line. 



b. The oviducts are a pair of slender tubes leading 



from the sacs of the ovaries, which unite to form 

 a much-convoluted duct surrounded by uni- 

 cellular-gland cells, and opening into the vagina. 

 The right oviduct passes under the nerve- 

 chain. 

 C. The vagina is a thick-walled tube, opening to the 

 exterior at the female genital pore in the second 

 annulus of the seventh somite. 



B. The Nervous System. 



The nervous system consists of a pair of supra-oesophageal 

 ganglia, a nerve-collar, and a double gangliated cord ex- 

 tending the whole length of the ventral body-wall. Prom the 

 ganglia nerves run outwards to the various parts of the body. 



E 2 



