U2 "TERRA NOVA" EXPEDITION. 



cere]>r;il organs. They then Ijccome separated l)y muscular tissue from the ventral 

 portion of the " U " (PI. II, fig. 4, V.B.S.), just as in L. rorrugafus, so tlint there are 

 for a short distance three apparently distinct spaces. Further back, the system of 

 intercommunicating vessels is not nearly so elaborately developed as in the former 

 species ; the blood-spaces round the gut are l)y no means so distinct or so numerous, 

 the most conspicuous being u pair of longitudinal vessels situated to right ;iim1 left of 

 the prosboscis-sheath, dorsal to tlie gut (PI. II, figs. 2 and 5, B.S.). A few smaller 

 and more irregular vessels can be seen laterally and ventrally. 



Sense-ort/cuis and A^ervoits Si/stein. — There is a minute " frontal organ " at the 

 tip of the snout, and the head is very abundantly supplied with gland-cells, some 

 of which are probably connected with it. 



The cephalic slits are very deep and straight-sided. There is very little expansion 

 at the bottom of the furrows, which communicate with the brain only at their hinder 

 ends. On the posterior wall of each slit there is a prominent transverse ridge, 

 containing a groove which leads into the canal of the cerebral organ. 



The upper extremity of the dorsal ganglion of the brain on either side ends 

 immediately in front of the cerebral organ. In the anterior and upper part of the 

 dorsal ganglia, the largest or "giant" type (Burger) of ganglion-cells are extra- 

 ordinarily well seen, and are of very large size in proportion to the whole brain. 



The cerebi'al organs (PI. II, fig. 4, CO.) are well-developed, large, and aliundantly 

 supplied with glands. On their inner and dorsal sides they are closely surrounded by 

 the lateral portions of the cephalic blood-sinus. 



The lateral nerves, with their investment of ganglionic cells, run out almost at 

 rio'ht angles to the long axis of the animal for a consideral)le distance on leavius; tlie 



iz> >::d c> o 



brain (PI. II, fig. 4, L.N.). and tlicn turn l»ack to run in tlie usual manner along the 

 sides. They are very stout, and lie somewhat towards the ventral side of the animal 

 (PI. II, fig." 2, L.N.). 



There is a complete plexus of nervous tissue (PL II, fig. 2, N.P.) immediately 

 outside the circular muscles of the body-wall, and a small dorsal nerve in this layer, in 

 the middle line, as in L. (■ori'U(jatns. 



Genital (Jiyaiis. — Li a female specimen examined, the gonads appear to form a 

 continuous series along either side of the worm (PI. II, fig. 5, O.). They comj^ress 

 the gut between them, and are not se})aratcd from tlieir neighl)ours liv aiiv 

 lateral gut-ca3ca. The eggs contained in this individual measure about ()■•_' nun. in 

 diameter. 



I am unable to give any account of the arrangement of tlie genital organs in 

 the male. 



Note : — It may be remarked that there is nothing in my description of tins form coiitradietory to tlie 

 supposition that it is identical with CerehratuIiiK validiis, Burger, from South Georgia. On the other hand, 

 the description (189.'5) of the latter species is ba.sed upon one specimen only, and is so brief that it would 

 be scarcely possible to determine the species from it, and moreover no figures are gi\i^n. Hence I have 

 not hesitated to regard the " Terra Nova " material in the light of a new species. 



