376 ON POLYCERCUS. 



Fig. 4. — Fully developed Cysticercoid in the uuextended condition, the 

 connection between the sheath of the rostellum (sh.J and the 

 edges of the aperture now established. Letters as in fig. 1. 



Fig. 5. — One of the hooks of the rostellum. Highly magnified. 



Fig. 6. — Cysticercoid, with the rostellum fully evaginated. 



Fig. 7. — Fully extended Cysticercoid. r, rostellum ; s, suckers; 6, "body"; 

 C.V., caudal vesicle. 



Fig. 8. — Transverse section through unextended Cysticercoid. a, central 

 tissue of rostellum ; b, layer of circular muscular fibres ; c, longi- 

 tudinal layer of muscular fibres ; d, sheath ; s, suckers ; t, wall 

 of cyst. 



Fig. 9. — Longitudinal section, h, hooks ; other letters as in fig. 8. 



