I90I W. A. BAILY— RHYNCHELMIS 313 



maturity, the ninth, tenth, and eleventh segments are seen 

 to contain each a pair of long vessels giving off a rich net- 

 work, which ramifies over the sperm sacs and the other 

 reproductive organs ; the intestine has a rich plexus, derived 

 from the paired non-contractile perivisceral trunks. The 

 ventral vessel consists, in the first five segments of the 

 body, of two separate halves, each half receiving the peri- 

 visceral trunk of its own side. 



" The testes, at first overlooked by Vejdovsky, were sub- 

 sequently recognised by him as two pairs of gonads in the 

 ninth and tenth segments ; as the worm gets to be mature, 

 the testes disappear, their contents being transferred to the 

 sperm sacs ; the same thing happens to the ovaries, which 

 lie in the eleventh segment. 



''Sense organs of epidermis: — The cells of the epidermis 

 are in part modified to form sense-organs. 



" In Rhynchelmis there are developed, at the breeding 

 season, continuous zones of sense-cells arranged in groups ; 

 the cells have the same elongated form that the sense-cells 

 generally show, and appear also to possess the fine pro- 

 cesses which arise from the epidermic cells. Vejdovsky 

 beheved that he could trace nerves into connexion with 

 these cells. 



" Net^ous system (Ventral nerve-chain) : — The commis- 

 sures which arise from the brain and embrace the gut 

 unite below it to form a ganglionated chain. This runs 

 from end to end of the body ; in the extreme posterior 

 region, where a regeneration of segments is going on, the 

 ventral nerve-cord may be often seen to lie in the thick- 

 ness of the epidermis ; otherwise it always lies in the body 

 cavity. The ventral nerve-cord gives off branches in each 

 segment. These branches arise in two different ways : in 

 the earthworms and many of the aquatic genera they arise 

 on either side of the nerve-cord and lie in the body cavity 

 for a greater or shorter distance until they plunge into the 

 thickness of the body wall. 



V2 



