REPORT ON THE NEMERTEA. 9 



application of the oesojDliageal epithelium against the muscular tissue most marked 

 (PI. IV. fig. 3), not even a basement membrane separating the two, whereas a suspension 

 of the intestine by means of the gelatinous tissue is of common occurrence in other 

 forms. The longitudinal sections prove that further back the intestine does not con- 

 tinue as a straight tube as it sometimes does in Palaeonemertea, but is constricted 

 (PL IV. fig. 2), the constrictions and resulting caeca being, however, much less marked 

 and prominent than in the Schizonemertea and Hoplonemertea. 



Eight and left of the intestine are situated the two longitudinal blood-spaces, which 

 are direct continuations of the blood-spaces already noticed in the head, and which com- 

 municate with these by passages that are encircled, together with the proboscis and its 

 sheath, by the annular nerve ring formed out of the right and left halves of the brain 

 and their superior and inferior commissures. 



The arrangement of these spaces has been fully described for Carinella by Oudemans,' 

 and I may refer to that description, the arrangement being on the whole very much the 

 same. There is no median dorsal blood-vessel in Carinina, and there is a very distinct 

 internal epithelium to the longitudinal blood-spaces, two of which are figured on PI. IV. 

 figs. 2, 5, 6. 



Transverse vessels of communication are not present in these two forms. I may 

 perhaps remark that my researches (XIV.) on the development of one of the Schizo- 

 nemertea have rendered it probable that also in the Palseonemertea we shall have to 

 look upon the blood-spaces in the same light as upon the cavity of the proboscidian 

 sheath, viz., as a direct derivative or continuation of the blastoccele, for which cavities 

 (in the adult state) I have proposed the name of archicoele. 



The nephridia are situated partly in the anterior portion of the blood-spaces, another 

 portion traversing the muscular body-wall and leading to the exterior. 



In the portion of the paired nephridia exclusive of this excretory duct we may 

 distinguish two distinct parts, one a continuous tube of varying dimensions, formed out 

 of very regularly arranged cells with large nuclei, but not in any way forming a series of 

 perforated cells such as are known in the nephridia of both Turhellaria and Discoj^hora, 



These cells are distinctly ciliated and figured on PL IV. figs. 4-6, Nc. The structure 

 of the second part of the nephridium is not so easily unravelled, and my preparations 

 of the two specimens do not suffice to reveal all the details. I find it to consist of 

 a cellular mass of spongy appearance protruding along a certain distance into the blood- 

 space, here and there giving evidence of a tubuliform structure, no internal funnels being, 

 however, anywhere recognisable (PL IV. figs. 4-6, N. sj).). 



I must here remark that the researches of Oudemans, who described in detail the 

 arrangement of the nephridia of Carinella and Carinoma,^ render it very possible that in 



* Quart. Journ. Micr. Sci., Suppl. volume, 1885. 

 - Loc. cit., p. 71, pi. i. figs. 4, 5 ; pi. iii. figs. 56, 57. 

 (ZOOL. CHALL. EXP. — FAKT LIV. — 1886.) Hbh 2 



