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



would appear as if there were two other longitudinal ones, situated right and left of the 

 proboscidian sheath (PI. VII. fig. 1). This may perhaps also turn out to be a special 

 feature of this species. 



Certain other peculiarities observed concerning the intestinal system must for the 

 present be passed over in sUence, for want of material to verify them. It may, however, 

 be added that the nervous plexus and the dorso-median nerve are much less conspicuous 

 (though present) in Eupolia australis than in Eupolia nipponensis, where the plexus is 

 in some places very thick (PI. VII. fig. 11). 



In this respect Eupolia australis more resembles Eupolia giardii, where the plexus 

 is not so very prominent, although the dorso-median nerve (PI. VII. fig. 4) is distinct 

 though not massive (c/.', PI. XL fig. 12). 



Eupolia nipponensis, n. sp. (PI. I. figs. 4, 5, 10; PI. VII. figs. 6, 11, 12). 



By this name I wish henceforth to designate a species of which fragments, partly 

 heads, partly posterior body regions, which obviously belonged to difierent specimens, 

 were collected by the Challenger in the Japanese waters. 



The series of sections reveal enough of common characters to deter one from assigning 

 the fragments to different species. 



The species is characterised by certain features already alluded to in the foregoing 

 description of Eupolia australis. If it resembles Eupolia giardii in the disposition of 

 the diff'erent layers of its integument, it difiers from this species in the absence of the 

 unusually thick circular muscular layer (PL VI. fig. 9) found in the oesophageal region 

 of the latter species. The deeper layers of the integument are most conspicuously 

 developed and vacuolated. 



That its nervous plexus is more conspicuous than that of the other Eiipolise was 

 noted before, and I may add that in the availaljle sections a very good horizontal aspect 

 was obtained of the brain-lobes, which showed these to differ in certain minor but still 

 easily verifiable points from those of Eupolia giardii. The upper lobe appears to be 

 much more cylindrical ; so does the inner fibrous core. There is no superior additional 

 gyrus to the superior brain-lobe with special fibrous core corresponding to what is 

 described and figured for Eupolia giardii (PL V. figs. 1, 5, 7-9 ; PL VI. fig. 8). 



The connection between the posterior brain-lobe carrying the ciliated canal and the 

 rest of the brain is, however, very intimate ; they are soldered together along a very 

 extensive surface. 



As to the proboscidian sheath, one of the sections clearly demonstrates how exceed- 

 ingly thin and delicate it is, and how the separation of its cavity from that of the 

 blood lacuna is even difiicult to observe. 



In this as in other species of Eupolia the distinction in the oesophageal epithelium 



