312 F. F. LAIDLAW : THE MARINE TURBELLARIA. 



PLATE XV. 



Fig. 10. Planocera armata. Transverse section across one of the gut branches, showing on its dorsal 

 side a pouch-like diverticulum, x 500. 



Fig. 11. Longitudinal median section through the genital apparatus of the same, reconstructed 

 from transverse sections. Somewhat diagrammatic, x 60. 



Fig. 12. Transverse section across the penis of the same at the level of the chitinous hooks, x 110. 



Fig. 13. Transverse section of the penis of Planocera langi at the level of the pair of large folds 

 projecting into the lumen. The section also passes through outer sheath and the 'recep- 

 taculum seminis.' 



Fig. 14. Transverse section through the penis of Leptoplana pardalis. 



Fig. 15. Longitudinal section through part of the oviduct of Pericelis hyerleyana, passing also 

 through one of the accessory uterine vesicles. 



Fig. 16. Section passing transversely through part of the oviduct of the same. 



Fig. 17. Transverse section through a tentacle of the same showing the very regular columnar 

 arrangement of the epithelium on the dorsal surface'. 



Fig. 18. Section through the penis of a specimen of Pseudoceros gamhlei. 



Fig. 19. Section through a dorsal papilla of Thysanozoon plehni showing the absence of any gut 

 diverticulum ; and the curious ' plug-like' mass of tissue (.r) at the tip of the papilla. 



Fig. 20. Section through the accessory vesicles of the penis and part of the antrum masculinum 

 of Prosthiostomum elegans. 



1 Indicated by the lettering c.e. 



