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



in another case they are at the sides of the head stretching backwards for a not incon- 

 siderable distance, but always exactly at the lateral margin, and because a glandular 

 epithelium plays an important part in their constitution, there is indeed some, though 

 of course very distant, analogy with the glandular parts of the posterior brain-lobes which 

 we have considered before. I do not wish to attach any importance or significance to 

 this analogy for the present, for we have no sufficient data ; but I mention it by way 

 of exjjlanation as to how I come to intercalate the description of these parts of the 

 organism in this place. 



The first structure which I have to mention occurs in the head of Drepanopliorus 

 lankesteri, and something analogous to it was noticed by former observers (XVI) in 

 Geonemertes palaeensis. In the Challenger specimen the horizontal sections through the 

 precerebral region demonstrate, when viewed with low powers, the presence of a lobulated 

 mass which is imbedded in the gelatinous ground-substance and partly traversed by 

 contractile fibres that radiate through the head in so many directions. When higher 

 powers are applied, this mass is dissolved into groups of cells enclosing more or less 

 circular free spaces, which, being present in consecutive sections, represent a system of 

 canals coated by the cells just mentioned, the whole forming a kind of spongy tissue. A 

 branch by which this canalicular system communicates with the exterior could not be 

 made out in my specimen, although von Kennel has found such an opening in his 

 Geonemertes, and thus I do not wish to lay too much stress on the fact of my being 

 unable to rediscover it in the only Challenger specimen in which I found this structure. 

 The cells are much more granular and at the same time larger than the surrounding cells 

 of the intermuscular gelatinous mass ; the nuclei are large and distinct (PI. XV. fig. 13). 

 It must 1-ie noted that the character of the cells and the aspect of the organ difier very 

 essentially from von Kennel's description. It is the situation that is correspondent. 



A similar precerebral glandular lobulated organ was found by me in Drejjanojjhorus 

 ruhrostriatus from the Mediterranean, though not in the Challenger specimens of this 

 species, in which, as was remarked above, the head was deficient. A special innervation 

 by nerve-fibres belonging to the cerebral nerves was in both cases made out. 



The second structure to which I alluded as occurring in Challenger Hoplonemertea 

 was found by me in the different specimens of Amphiporus moseleyi, both in transverse 

 and horizontal sections. It may shortly be characterised as being an accumulation of 

 short, saccular tubes, blind posteriorly and opening to the exterior by a distinct neck, 

 which pierces muscular layers as well as basement membrane, its internal epithelium then 

 fusing with the integument. These short flask-like sacs sometimes internally coalesce 

 with each other, the same interior cavity then communicating outwards by more than 

 one duct. This, however, appears to be more or less exceptional. They are very 

 numerous, though short, at the tip of the head (PI. X. fig. 3, gl.s). They become larger 

 when we follow them further backwards, where we find them situated laterally in that 



