574 ON SOME SOUTH PACIFIC NEMERTINES COLLECTED BY DR WILLEY. 



oesophagus passes into the mid-gut in the posterior brain region (Fig. 23), though before 

 this happens a well-marked typhlosole-like process is found projecting from it in the 

 mid-ventral line (Fig. 23, oes.t.). 



The proboscis shews the structure typical for the genus and contains 31 nerves. 



The excretory pore is situated "35 mm. behind the cerebral organ. The whole 

 extent of the excretory system is about 2'2 mm. of which one-seventh lies in front of 

 the pore, so that the excretory tubules do not reach quite to the cerebral organ. Near 

 the pore the excretory duct dilates into a bladder. 



The diverticula of the proboscis sheath commence at the termination of the cerebral 

 organ. They are rather narrow and reach round the intestinal pockets about half-way 

 between the nerve cords and the mid-ventral line. 



The brain is large and in shape differs greatly from that described by Burger 

 for D. liitus. Instead of being " schlank, elliptisch, von geringeren Querdurchmesser, 

 aber aussordentlich hoch," it is well rounded (Fig. 23). The ventral commissure is 

 extraordinarih' strong (Fig. 22). 



The cerebral canal opens exactly laterally, not somewhat dorsally as in D. latits. 

 The cerebral organ is large and ends at the same level as the dorsal ganglion, i.e. 

 no part of it lies behind the brain. It possesses a layer of gland cells on its ventral 

 surface, which glandular structure does not project backwards from the rest of the 

 organ as in some other species, e.ff. D. willeyanus (Fig. 19, gl.). The pigment masses 

 in the cerebral organ are comparatively very large (Figs. 24 and 27), and were visible 

 in the living animal (Fig. 26, c.org.). 



The parenchyma is well developed, being particularly dense where it surrounds 

 various organs such as the nerve coi'ds, excretory tubules, etc. (which indeed have 

 shrunk away from it in conservation). In the light of Dr Willey's observation that 

 this animal swims about freely such a fact becomes of interest when we regard such 

 a form as Pelagonemertes where free-swimming pelagic habits are accompanied b}' 

 an enormous development of the parenchyma. Possibly the substance serves to take 

 the place of a skeletal structure enabling the relatively slightly developed muscular 

 layers to bring about sharjj vigorous contractions in definite directions resulting in 

 forward propulsion. 



HETERONEMERTINI. 



4. Eupolia rugusa, n. sp. PI. LIX. Fig. 2S and LX. Figs. 29—31. 



A single specimen was taken at Xew Britain. It measured about 3 cm. in 

 length (Fig. 31) and the skin in the preserved specimen was deeply wrinkled. Dr 

 Willey tells me that these wrinkles were present when the worm was living, and I 

 have accordingly given it the name which stands at the commencement of this 

 description. In the characters and ari-angement of the skin, cutis, and muscle layers 

 the animal presents no marked divergence from the general type of the genus. 



The head glands are enormously developed. They open at the anterior margin 

 of the proboscis pore which is ventrally situated. Lying in the outer longitudinal 



