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



dealing with the anatomy of the group. It is wholly continuous, and a body-cavity in 

 which the above-named organs may be said to float, or to be suspended, is totally absent. 



A rapid survey of the peculiarities which these five systems present must complete 

 this descriptive account of the new genus. The aperture for the proboscis, which is 

 situated terminally, leads into an anterior cylindrical compartment, which remains passive 

 when the proboscis is protruded or retracted. It is coated by ciliated cells, and at the 

 posterior end the anterior insertion of the proboscis into the body musculature takes 

 place (PI. II. fig. 8 ; PI. III. fig. 5). Although the name is etymologically not wholly 

 adapted for the purpose, I still am inclined to adopt for this compartment, which is 

 present in all Nemertea, the name of rhynchodseum. This name as clearly separates it 

 from the cavity of the proboscis or its sheath, as that of stomodseum and proctodseum 

 distinguishes certain portions of the intestine of other invertebrates from the mid-gut. 



The rhynchodseum of Carinina has a great resemblance to that of Carinella, more 

 especially because of the wide and much distended blood-space which wholly surrounds 

 it, and in which it is kept in place by numerous strings of tissue starting from the 

 muscular body- wall and inserting themselves on the muscular investment of the 

 rhynchodseum (PL III. fig. 5 ; cf. IX., pi. i. fig. 2). From the same figure it may be 

 gathered that the internal cellular coating of the rhynchodseum is more than one row 

 of cells thick, and that these cells have a clear and distended aspect, with a comparatively 

 small nucleus. 



The proboscis itself is inserted in a very simple way in the muscular tissue of the 

 body-wall. The muscidar investment of the proboscis curves round at an angle of 90°, 

 and becomes continuous with the longitudinal muscular layer of the body-wall. The 

 details of this arrangement may be gathered from PL III. fig. 5, and it will there also be 

 seen how the protruded proboscis remains fixed to the body all along this annular point 

 of attachment. Thence it extends backwards as far as the proboscidian sheath permits, 

 which, in the forms allied to Carinella, is only the anterior portion of the body. It is 

 drawn back again by its retractor. How far backwards the proboscidian sheath reaches 

 in Carinina could not be made out, as I only possessed two small anterior fragments, 

 in neither of which the proboscidian sheath terminated. The proboscis itself could be 

 examined with detail in the single specimen which was cut longitudinally. An anterior 

 and a posterior portion of different textures are exceedingly distinct. They are separated 

 from each other by a constriction. In the posterior portion the cells are eminently 

 glandular, high and flask-shaped ; in the anterior portion they are less high and appa- 

 rently less glandular (PL III. figs. 1, 2). Great differences in aspect, but not in actual 

 texture, are of course occasioned by the different stages of contraction in which the various 

 parts of the proboscis happen to be. 



The mouth, situated ventrally close to the anterior extremity, was very small in both 

 specimens. The cellular coating of the oesophagus is very distinct, and the direct 



