PLATE XX. 



Fig. 



1. Transverse section of the oesophageal region of Lineus gesserensis after the channel has 



attained full development. X 55 diam. 



2. Transverse section of the oesophageal region of a large specimen of the same species in 



which a favourable view of the vascular meshes (u) around the cavity is obtained, v, one 

 of the larger spaces on each side of the sheath for the proboscis. X 55 diam. 



3. Transverse section of a fine specimen of L. gesserensis some time after spawning, and 



when the animal has regained its plump condition. The shriveled traces of the repro- 

 ductive organs are seen at ov. A doubling of the proboscis in its sheath has occurred. 

 X 40 diam. 



4. Transverse section of the proboscis of Micrura fusca. a, external coat ; b, great longi- 



tudinal muscular layer ; c, belt of circular muscular fibres ; d, basement-layer - e, in- 

 complete series of longitudinal fibres which do not occur in the common species; 

 /, glandular mucous coat ; g, peculiar lozenge-shaped portion of longitudinal fibres, formed 

 by the splitting and crossing of two bands from the circular muscular coat ; /, separate 

 segment at the other pole of the circle. X 90 diam. 



5. Transverse section of the proboscis of Meclcelia asulcata. a, external spiral coat; b, longi- 



tudinal layer ; c, central cavity surrounded by the glandular coat ; d, cross of fibres at 

 the poles. X 210 diam. 



6. Transverse section of the proboscis of Carinella annulatci* X 90 diam. 



7. Gland-cells from the wall of the digestive cavity of Amphiporus lactifloreus. X 400 diam. 



8. One of the same slightly compressed glands. X 700 diam. 



9. Contents of the former, with oil-globules. X 700 diam* 



10. Pseudo-navicellee extruded with the former parasites from the digestive canal of Lineus 



sanguineus. X 350 diam. 



11. Portion of a gelatinous cord containing ova from the digestive canal of L. gesserensis. 



X 180 diam. 



12. Ovum from the same. X 350 diam. 



13. Transverse section of the body- wall in the region of the lateral nerve of a Lineus from 



Fetlar, showing the intricate arrangement of radiating fibres which pass through the cir- 

 cular coat and divide the external longitudinal muscular layer into endless fasciculi. 

 X 90 diam. 



