23 
Rostellum. — The rostellum is a sac-like body embedded in 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 
24 
Fig. 22.— Proglottid of T. viurinaDn]. {=H.nana). 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. Upon retraction the 
anterior part of the rostellum containing the inner sac is drawn 
