TTFE ANNBLIDA. 



245 



likewise surrounding the oesopliagus and apparently represent- 

 ing the supraoesophageal ganglion. Numerous longitudinal 

 nerves pass forward from the ring to imite with another ring 

 around the base of the proboscis from which nerves pass to 

 the tentacles. Below the intestine lies a large ganglionic mass 

 with which the circumoesophageal commissures unite and 

 which gives off a number of peripheral nerves. This mass is 



mo 



Fig. 111.— Myzostomum (after von Geapf). 

 c = cirrus. r = rectum. 



elo = cloacal opening. s = stomach. 



fo = opening ot uterus into cloaca. su = sucker. 

 = opening of male reproductive organs. t = testes. 

 p = parapodium. u = uterus. 



p7t = proboscis. 



composed of several (probably 6) united ganglia and represents 

 the ventral nerve-cord of other Annelids. Nerves pass pre- 

 sumably from the supraoesophageal ganglion-cells along the 

 dorsal wall of the intestine and seem to constitute a sympa- 

 thetic system. The only structures which can be considered 

 sense-organs are the marginal cirri and the tentacles of the 

 proboscis, which probably have a tactile function. No traces 

 of eyes have yet been observed. 



Nephridia, unless they be represented by the sucker-like 

 depressions and the oviducts, are wanting. The Myzostomese 



