26 
and in their new position make up the mass of the longitudinal muscle 
layer. Transverse muscle hbers. if present, are very few and weaklv 
developed. Dorso-ventral fibers are likewise insignificant. 
Excrktorv system. — There are two pairs of lateral longitudinal 
excretory vessels (figs. 32, 33) which unite in the scolex to form an 
anastomosis at the base of the rostellum. Two small closed loops 
extend into the latter, one on either side (Ming'azzini, 1899), similar 
to the loops found in Ilyrnenolepis diniinuta (p. 88) and Hymenolefis 
30 31 
Fig. 30. — Posterior end of II. nana -with sterile proglottid (third from top): camera drawing of 
stained preparation. Enlarged. (After Miura ct Yamazaki, 1897, pi. 14, fig. 7.) 
Fig. 31. — Portion of strobila of IL nana. Enlarged. (After Stein, 1882. pi. 12, fig. 12.) 
carioca (see Eansom. I90i?). The A'entral vessels are larger than the 
dorsal throughout the strobila. and are united in the posterior portion 
of each segment by a transverse vessel. 
Reproductive sy'STem. — The sexual organs become evident as 
indistinctly defined masses of cells shortly after the first apparent 
strobilation (fig. 25). Toward the middle of the worm they are in a 
state of active sexual maturity. The male organs develop much more 
rapidly than the female organs, and become active earlier. As is 
common among tapeworms, they occupy more especially the dorsal 
