REPORT ON THE NEMERTEA. 65 



between these bundles, and also carries in the nephridial regions the terminal deferent 

 portions of the nephridial ducts (PI. VII. fig. 5, Nep). The originally cellular nature of 

 this connective tissue is retained in the head and in the anterior portion of the trunk, 

 where the outer longitudinal layer of muscles is not less thick, but certainly contains a 

 very much smaller number of fibres, because of the permanence of the intermuscular 

 cellular stroma just alluded to. A. comparison of figs. 2 and 3, PL VII., the one taken 

 through an anterior, the other through a more posterior region of the trunk of a Eupolia, 

 will elucidate this, as will also the comparison of fig. 5, PI. VII., with the more enlarged 

 fig. 6 of PL X. (taken from the same specimen), which represents a section through the 

 region marked Bet in the former figure situated further forwards, and thus decidedly cellular 

 as far as concerns the intermuscular tissue. One important fact is clearly indicated in this 

 latter figure, viz., that the cells situated between the muscle bundles of the outer longi- 

 tudinal layer (y.vl), although their general aspect, vacuolation and arrangement very 

 much resemble that of the similarly vacuolated cells of the deepest layers of the integu- 

 ment {Jdrf), may nevertheless be immediately distinguished from these by their much 

 larger nucleus. The same fact follows quite as unmistakably, though somewhat less clearly, 

 from PL VII. fig. 2. It gives some support to the hypothesis, that the whole of the deeper 

 cell-rows of the integument, vacuolated or otherwise, being substantially different from 

 the subjacent mesoblast cells, may be looked upon as epiblastic. However, this question, 

 which pertains more to an ontogenetic than to an anatomical investigation, may safely 

 be left out of further consideration. This basement tissue of Eupolia, much less 

 regularly arranged than in Hoplonemertea and in the Carinellidse, is thus still directly 

 homologous with that of the latter. 



A secondary external homogeneous basement layer is found immediately below the 

 outer stratum of unicellular glands of the integument ; in the paragraph devoted to the 

 integument the comparison with Carinina, Carinella and Carinoma has been already 

 instituted, and it was at the same time shown in what way these different arrangements 

 may be identified with one another. 



In the anterior portion of the body the stratified basement layer Bet (PL VII.) fuses 

 with the sparse intercellular tissue that is present round the vacuolated cells, and 

 appears to be a direct continuation of it. In the posterior portion, however, where the 

 muscular bundles are more strongly developed, this stratified tissue appears more limited 

 to the region between the muscles and the integument, principally because here the 

 character of the intermuscular tissue is also changed and becomes more homogeneous, 

 although it is here and there traversed by radial fibres, is also provided with nuclei, and 

 contains numerous nerve-tracts. The general aspect, and the effect of the staining 

 reagents, show this intermuscular tissue to be identical with the homogeneous, 

 more or less gelatinous tissue, that is observed between the outer longitudinal 

 bundles of Carinina (PL III. fig. 6). The cells, of which traces are found 



(ZOOL. CHALL. EXP. — PART LIV. 1887.) Hhll 9 



