PLATE XIV. 



Fig 1. Cerebratulus angusticeps, n. sp. The medullary nerve (m) and the transverse paired metamerical 

 nerve-stems (trn). Drawn with the camera. 1 mm. on the same scale is indicated on 

 the left of the figure. 



Fig 2 Cerebratulus corrugatus, M'Int. Transverse section of the lateral nerve-steni (IN) and body-wall 

 a 8, y, the muscular layers ; B, the primary hasement membrane, and J, the integument. 

 in outline (cf. PL XIII. fig. 6); rf, radial fibres piercing the muscular layers ; n and pn 

 nerve-tracts; of which one (pn) is seen to emerge directly from the lateral nerve-stem and 

 to innervate the sensory layers of the integument ; npl, nerve-plexus. 



Fig. 3. Cerebratulus corrugatus, M'Int. Diagrammatic figure of a transverse section in the mouth-region 

 to show the innervation of the oesophagus and blood-lacunas. OeE , the oesophageal 

 epithelium; Prs, the proboscidian sheath; co.l, the circumcesophageal blood-lacuna. In 

 the nerve-plexus, which is indicated by a black line, m marks the medullary nerve, and 

 nl, the lateral nerve-stems; vi.n, the visceral branches springing from the plexus; n.ra, 

 the vagus ramifications transversely cut and intermixed with the branches vi.n. 



Fig 4. Cerebratulus corrugatus, M'Int. Part of the same section as fig. 3, more considerably enlarged. 

 Lettering as in fig. 3; npl, nerve-plexus ; rf, radial, not nervous fibres ; a./3.y, the muscular 

 layers; co.l, the blood-lacunas with cellular coating. The oesophageal epithelium (oe.E) 

 is not represented in its whole thickness. 

 Fig 5. Cerebratulus parkeri, n. sp. Diagram, drawn with camera, of the inferior brain-lobes, fir and 

 the vagus nerve (va) springing from them, the two stems being united by a series of trans- 

 verse commissures co close to their origin. The brain-lobes merge into the lateral nerve- 

 stem (N) ■ the ventral metameric connections of the latter are indicated by dotted lines, 

 v.tr.n, those of the brain-lobes being lettered c.tr.n; Oe, outline of the oesophageal 

 epithelium. 

 Fig 6 Cerebratulus angusticeps, n. sp. Horizontal section of the left upper and posterior brain-lobes 

 (Br and PBr) • col, cl, the free blood-lacuna between the bram, the proboscidian sheath, 

 and the oesophagus, the boundaries of these' two latter being only indicated by dark shading ; 

 a, 8, muscular layers; In, anterior portion of lateral nerve-stem, the ganglion cells of the 

 cellular investment being here cut; cc, the outwardly directed portion of the ciliated 

 canal inside the posterior brain-lobes; cc', cc", the deeper portion of the same being cut 

 in two places, because of the S-shaped curve which this canal makes inside the brain-lobe. 

 The relatively large size of the posterior brain-lobe, and the preponderance of fibrous 

 nerve-tissue in the upper lobe, are indicated in this figure. 

 Figs 7, 8. Cerebratulus mmroren, n. sp. Two transverse sections (a few sections apart) through the 

 posterior brain-lobe audits investment of large granular glandular cells (g.cl). m, the 

 outer membranous investment of the lobe; n.cl, the ordinary ganglion cells with fibrous 

 core in the centre of the lobe ; cc, the ciliated canal with an epithelium of its own, more 

 distinct in fig. 8 than in fig. 7. 

 Fig. 9. DrepanopTiorus lankesteri, n. sp. Part of a horizontal section through the upper bram-lohe, with 

 interior fibrous cote (cf.) and outer layer of ganglion cells, n.cl ; a few of which aie much 

 larger (nCl). 

 Fi. 10 Drepanophorus lankesteri, n. sp. Part of a horizontal section through the posterior brain-lobe^ 

 °' Bm the outer investment of the lobe ; n.cl, the nerve-ceUs ; cc, the ciliated canal with 



its Epithelium ; gel, the granular glandular cells ; the anterior ones pouring their contents 

 into the lumen of the ciliated canal. 

 Fig 11. Cerebratulus macroren, n. sp. Part of a transverse section through the ^showing the .ciliated 

 canal to the posterior brain-lobe in its course from that lobe (PBr) to the exterior 

 gel, the granular glandular ceUs ; cc, the lumen of the canal coated by an epithelium of 

 varied histological character as we pass outwards towards E, the external layer of the 

 integument. At gl. a sort of ring-shaped cushion of peculiar cells may be said to 

 embrace the canal (cf., PL VI. figs. 1-3). Just behind this the epithelial cells are very 

 closely set and provided with elongated nuclei, further backwards they are seen to pass 

 without any sudden transition into those lining the canal, inside the brain-lobe. 



