23 
Rostellum. — The rostellum is a sac-like body embedded iii the axial 
portion of the head between the four suckers. Its wall is formed 
b}" a membrane which is continuous with the cuticula at the anterior 
Fig. 22. — Proglottid of T. ?Ji wina Duj. (= if. ??a??a). Enlarged. Copy of original type figure. (After 
Dujardin, 1845a, pi. 12, fig. A5.) 
Fig. 23. — Proglottids of II. nana; a, showing ovary; b, containing eggs in course of formation; c, 
gravid. (After Leuckart, 1863, p. 396, fig. 114.) 
Fig. 24. — Proglottid of H. nana showing reproductive organs. Enlarged. (After Leuckart, 1886a, 
fig. 409A.) 
surface of the head. The protrusible portion is occupied by a second 
smaller sac likewise limited by a membrane. L^pon retraction the 
anterior part of the rostellum containing the inner sac is drawn 
