466 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 58. 



Fig. 16. — Optical section through anterior extremity of a young male, showing 

 details of the receptacle and its associated structures. 



17. — A portion of the body wall in the region of one of the lateral nuclei, 

 showing the relation between the size of the nucleus and the width 

 of the animal and the relations of the nucleus to the lacunar sys- 

 tem. From a young male, 



18. — A nucleus similar to the one shown in preceding figure but from a 

 larger, older female. 



19. — Posterior extremity of a young female in optical section, showing sub- 

 terminal location of genital opening. 



