ON ONCHNBSOMA STEENSTRUPII. 233 



Fig. 8. — Transverse section through the introvert, showing the layers of 

 the skin, the cesophagus, retractor muscle, and ventral nerve-cord. The 

 body-cavity contains corpuscles and sperm morulse. 



Fig. 9. — Longitudinal lateral section of the extended introvert, showing 

 mouth, oesophagus, and thickened ciliated lip, with the circum-oesophageal 

 nerve of each side. 



Fig. 10. — A section of the brain, parallel to the preceding (fig. 9), but more 

 dorsal. It shows the distribution of the ganglion-cells and fibres in the brain, 

 and the three main nerves given off from it ; also the insercion of the retractor 

 muscle, and one of the recesses formed by the crumpled nature of the 

 cesophagus. 



Fig. 11. — Diagram representing the arrangement of parts in the head, 

 which is supposed to be divided medianly. The right half only is shown. 



Fig. 12. — Section through the head and brain. The introvert is retracted. 

 The section is not quite in the middle line, and does not show the connection 

 of the brain with the epidermis. 



VOL. V, PART II. 



