26 R- C. Punnett. [No. 2 



17. Cerebratulus longifissus (Hubrecht, 1887). 



Localities. Hjeltefjord near Bergen, from about 50 metres on hard 

 bottom covered with fragments of mussel shell. 

 Alverstrøm (mouth of) near Bergen, from 80 metres on shell 

 sand. 



Occurrence. Fragments of several specimens from each locality. 

 Not uncommon. 



External features. A very thick massively built worm measuring 

 about 6 — 8 mm. in diameter. No complete specimen was 

 obtained so that the length cannot be given with any certainty. 

 Judging from the fragments it would probably accord very 

 closely with that of Hubrechfs specimens 1 ). The worm is 

 characterized by the exceedingly long head slits (Pl. I, fig. 15) 

 which reach along the side of the body as far as the intestinal 

 region (Pl. II, fig. 22). Colour both in life and after preser- 

 vation pure snow-white. In the head the brain shews pink 

 through the body wall. The worms are exceptionally sluggish 

 in their movements. The specimens captured shewed a strong 

 tendency to form a tube of the shell sand in which they were 

 living. Possibly their sluggishness may be correlated with 

 tubicolous habits as in Euborlasia. As the anatomical account 

 given by Hubrecht is somewath meagre I have given below a 

 fuller account of this interesting species. 



The body wall is very thick. The epithelium, which contains a 

 number of deeply staining unicellular glands in its deeper portion, 

 and numerous rhabditiform bodies more externally, rests on a 

 fine basement membrane (Pl. I, fig. 5). Beneath the basement 

 membrane are a few circular muscle fibrils. The cutis glands 

 are well developed and between them and the outer longi- 

 tudinal muscle layer is a thick layer of gelatinous connective 

 tissue. The relative thickness of the different muscle layers 

 is shewn on Pl. I, fig. 2. 



The proboscis was unfortunately missing in all the specimens procured. 

 The proboscis sheath is short not being found in the intestinal 

 region some way from the posterior end. 



The vascular system shews a cephalic loop, the two limbs of which 

 are connected by irregular anastomoses over the rhynchodaeum. 



The excretory system is somewhat small. The tubules are found 



') Hubrecht, Nemertea, Challenger Eeports 1887. Pl. I, fig. 16. 



