12 THE VOYAGE OF H.M.S. CHALLENGER. 



Eupollse, I suppose that this constriction is not so marked in the living animal, but that 

 here, as in the Mediterranean species, two very shallow, strongly ciliated grooves in the 

 integument, curving laterally round both sides of the head, were present, and that, during 

 the process of preservation in spirit, the fold just mentioned made its appearance in the 

 region where normally these transverse grooves are situated. 



What immediately distinguishes Eupolia giardii from its congeners is the thickness of 

 the circular muscular layer in the oesophageal region. 



In M'Intosh's preliminary MS. notes on the Challenger Nemertea, I find the 

 following remarks upon this specimen, which he perfectly recognised as a new species 

 (the sjjecific name giardii is taken from M'Intosh's provisional label), without, however, 

 at that time referring it to delle Chiaje's Mediterranean genus. 



" A comparatively large form, measuring about 40 mm. in length, with a diameter in 

 its widest part of 6 '5 mm. This specimen is colourless, bluntly rounded at each end 

 and somewhat fusiform in outline. 



" The anterior end is almost truncate, with a dimple in the middle, caused by the 

 proboscidian aperture, and there are traces of a transverse and a vertical groove, thus 

 forming a cross at the tip of the snout. 



" The latter is separated from the body by a well-marked fold which probably indicates 

 a furrow, and which on each side does not quite reach the mouth. The mouth occurs on 

 the ventral surface somewhat behind the foreo-oing; furrow and in the form of a triangular 

 dimple. A small aperture (anus) is situated at the dorsal margin of the blunt posterior 



end The small size of the proboscidian slieath is remarkable. It has an 



external layer of circular fibres and an inner layer of longitudinal muscular fibres. Both 



are thin. It is continued to the posterior third In the middle and towards 



the j)osterior third the body-wall presents a decided change from the foregoing — the 

 alimentary cavity forming a large central space and the solid wall is considerably 

 diminished in proportion." 



In studying the sections of this species several additional points of interest came to 

 light. Those concerning the brain-lobes will be discussed in the paragraph treating of 

 the nervous system in general; the general aspect of the brain as it may be gathered 

 from a reconstruction of the sections is figured on PL V. The outline of the whole of 

 the lobes and that of the internal fibrous core are here figured side by side in order to 

 show the relations of the parts and the actual position of the ciliated canal that penetrates 

 into a separate part of tlie brain-lobes more clearly. There is a terminal commissure 

 between the longitudinal nerve-stems below the anus (PI. VII. fig. 8). 



The right and left longitudinal nephridial ducts (PL VI. fig. 9, Nep.) communicate 

 by deferent ductules (PL VII. fig. 5, Nep.) with the exterior. Of the latter there are 

 several; in the available transverse series through the head and oesophageal region I 

 count five to the left and seven to the right, some of these (sections 298-325 left and 



