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



also lettered B on PI. VII., but to be so with the deeper layer, Bet of the latter plate ; 

 and (2) in comparing the glandular structures of Carinina more especially with the 

 deeper layer of glands of Eupolia, and in looking upon the unicellular glands of the 

 latter as more particularly developed in the outermost layer. These latter are then 

 comparable to the smaller and superficial unicellular glands which are met with in 

 Carinina {PI. IV. fig. 1). Similar considerations concerning the homology of the diff'er- 

 ent portions of the integument can be applied, as we shall see in the sequel, to the 

 Schizonemertea, their integument in so many points resembling that of Eupolia, and 

 being thus also linked to that of Carinina by intermediate forms, such as Carinoma. 



Amongst the Hoplonemertea it is most difficult to obtain specimens in which the 

 integument is in a fair state of preservation. Even in the specimens that have been 

 treated with special care, it is a rare occurrence to find a portion of the integument in 

 which its difierent layers can be clearly made out. 



From what I have noticed in the Challenger specimens, there is a certain amount of 

 uniformity which must first be noticed and compared with what obtains in Paleeonemertea 

 and Schizonemertea. Sharply distinct from the basement-membrane, which, after removal 

 of the integument, would even show a more or less honeycombed surface, are the deeper 

 eel] -layers of the integument, the rounded bases of these cells fitting into the honeycomb- 

 like pits in the basement-membrane just alluded to (PI. X. fig. 2). These cell-layers, 

 with very distinct nuclei, are in thin sections many rows thick. The nuclei are, however, 

 never so close together as they are in the subsequent layer, which is generally situated 

 about halfway between the basement-membrane and the ciliated surface (PL X, fig. 1). 

 On teasing out the elements of this layer, we find long spindle-shaped cells, considerably 

 thinning out at the ends, and only bulging at the spot where the deeply stained nucleus is 

 situated. Tliese nuclei, again arranged in several rows even in the thinnest transverse 

 sections, are there disposed so as to fit close between each other, the thin ends of the cells 

 being directed one towards the outer surface and the other towards the deeper layers 

 before mentioned. It cannot be doubted that sense-cells, which very generally have a 

 similar shape and position, are among these (cf. Dewoletzky, II). Towards the outer 

 surface, the remaining stratum of the integument has the peculiar radially streaked 

 appearance already described for the Palseonemertea ; nuclei being rarer in this layer 

 than in the two foregoing. Finally, the cilia are implanted upon the outer margin of 

 this region, and teased preparations reveal the presence of special cells with a nucleus of a 

 very much paler hue, and very faintly coloured. Only in a few preparations have the cilia 

 been well preserved ; a cuticula upon which they are implanted, as elsewhere (XIV) 

 described in embryonic stages, was also only noticed in certain favourable sections. 



These are the principal features marking the integumentary system of the Hoplone- 

 mertea. A few further details, however, may still be added. The deepest layer (PI. X. fig. 2) 

 contains fibrous nerve elements, not distinctly indicated in the figure. The absolute 



