PLATE XII. 



Fig. 1. Cerebratulus macroren, n. sp. Transverse section through a part of the brain-lobes of the New 

 Zealand specimen. The medullary nerve (m) is still in connection with the brain-lobes (hi); 

 prs, the proboscis, passing between the nervous ring formed by the brain-lobes and their 

 commissures. Superiorly two bundles of longitudinal muscle-fibres are enclosed by the 

 brain-tissue. 



Fig. 2. Cerebratulus macroren, n. sp. Transverse section of the body-wall in the region of the lateral 

 nerve-stem (Japanese specimen). a./?.y, the three muscular layers, the latter with the deeper 

 integumentary glands embedded between the muscle-bundles (r/. PL XL figs. 10, 11); pi, the 

 nerve plexus ; b, the secondary basement membrane with the thin layers of integumentary 

 muscles just below it ; J, the cellular integument ; N, the lateral nerve-stem, into the fibrous 

 core of which part of the fibres of the plexus may be seen to be interwoven. 



Fig. 3. Cerebratulus corrugatus, M'Int. Transverse section of the medullary nerve (m) at a point 

 where a pair of transverse stems (of. PI. XIV. fig. 1) merge into it. n, these nerve-stems 

 (being thickened tracts in the plexus, ^>Z); pf, nerve fibres radially emerging from these tracts 

 and having the significance of sensory or motor peripheral twigs ; ./?, radial fibres (not 

 nervous) piercing the plexus (cf. PI. XIII. figs. 3, 4, rf). 



Fig. 4. Cerebratulus corrugatus, MTnt. Transverse section of the medullary nerve of another specimen. 

 Lettering as in the foregoing figure. 



Fig. 5. Drepanqphorus lankesteri, n. sp. Transverse section of the lateral nerve stem (iV), with two 

 peripheral nerves, pf, springing from it. The fibres of the latter partly emerge from the 

 ganglion cells, partly from the fibrous core of the lateral stem. 



Fig. 6. Drepanopliorus serraticollis, Hubr. A portion of a transverse section through the proboscis. /./', 

 the longitudinal muscle-fibres, in two strata, between which lies the nerve-plexus np, of 

 which In is one of the longitudinal thickenings (nerve-stems) ; ox, the outer ; i.c, the inner 

 layer of circular fibres ; b, transparent basement tissue. 



Fig. 7. Cerebratulus macroren, n. sp. Transverse section of the superior nervous connection between 

 the two brain-lobes (Japanese specimen). Nerve cellular elements predominate in this region 

 whence the medullary nerve is continued both backwards and forwards, nl, the homo- 

 geneous layer forming an investment to the nerve-tissue ; pre, the proboscidian sheath in 

 outline. 



Fig. 8. Cerebratulus macroren, n. sp. A few sections further backwards. The medullary nerve m is 

 here more distinct, its anterior continuation m' being on the point of coalescing with it. 

 Lettering as in fig. 7. pr, outline of the proboscis ; Br, fibrous core of the brain-lobe. 



Fig. 9. Cerebratulus medullatus, n. sp. Transverse section of the medullary nerve (m). pi, the plexus ; 

 )3 and a, the circular and longitudinal muscular layers ; (inner circular muscular fibres 

 are seen to form the outer layer of the proboscidian sheath) ; prn, the proboscidian sheath 

 nerve, receiving delicate fibres from the medullary nerve and situated just above the pro- 

 boscidian sheath musculature. 



Fig. 10. Cerebratulus medullatus, n. sp. Integument and muscular body wall. Lettering as in fig. 2. 

 dgl, the deeper glands of the integument enclosed in the musculature. 



