2 88 DISCOVERY REPORTS 



body cavity ventrally and finally open into a short median anterior caecum ending 

 blindly forwards. 



The rhynchocoel is spacious but the wall is thin. It is composed of inner longitudinal 

 and outer circular muscles and extends nearly to the end of the body. The proboscis is 

 thin and the muscles are poorly developed. It possesses seventeen nerves. 



Fig. 65. Probalaenanemertes irenae, n.sp. Transverse sections. A, the region of the brain; 

 B, mid-body; C, tail. In, lateral nerve; ov, egg. 



The brain is fairly large, dorsal ganglia rather larger than ventral. The lateral nerves, 

 containing a distinct mass of fibres from the dorsal ganglia, are pressed ventrally until 

 they rest against the muscles of the body wall and close to them towards the middle line 

 the gonads begin development. The eggs are immense (Fig. 65 B). 



NOTES ON THE DISTRIBUTION OF THE 

 SOUTHERN NEMERTEANS 



The extension of the Mediterranean fauna to the south western extremity of Africa 

 has already been indicated. Certain species, of course, can be reckoned as cosmopolitan 

 and their occurrence leads to no comment; for instance, Linens ruber, Tetrastemma 

 candidum and Amphiporus pidcher, which have been found widely distributed in the 

 temperate seas in the northern hemisphere: but the inclusion of Tabidamis nothus, 

 Nemertopsis tennis, Linens bilineotus and Cerebratidus fuscus — all easily identified by 

 striking colour, markings or body form apart from their anatomy — points to a com- 

 mon origin with the fauna of the Mediterranean even if there is discontinuity across the 

 equatorial region where at present the littoral fauna is not known. That more records 

 are not available from southern waters is probably an expression of the relatively little 

 systematic work that has been done south of the equator in comparison with the 

 northern coast lines. Amphiporus pidcher has been recorded from Chili (Isler), Tubulanus 



