86 PLATYHELMINTHES CESTODA CHAP. 



of longitudinal excretory vessels are present, usually connected by 

 transverse ducts and opening by a single terminal pore. Occa- 

 sionally a regularly paired arrangement of lateral or secondary 

 pores is present (Figs. 38 and 41 , for. sec). Flame-cells occiir at 

 the end of the fine tubules (Fig. 38), and the whole system is 

 well developed, but may undergo degenerative changes in the 

 older proglottides. The central nervous system varies according 

 to the degree of differentiation of the rostellum ; and, owing to 

 the difficulty of staining the nerves and the contradictory state- 

 ments of authors, we do not yet possess a fully reliable account 

 of the nervous system even of the commoner Taeniae. Free 

 nerve endings and other sensory terminations have been recently 



Fio. 41. Diagrammatic transverse section of SchistocepJialus solidus Crepl., from the 

 Wild-duck, illustrative of the Cestodes with uterine aperture (uto). x 12. cs, 

 Cirrus-sac ; for. sec, one of the paired lateral openings of the excretory vessels ; In, 

 longitudinal nerve ; ov, ovary ; ovd, oviduct ; par.m, parenehymatous muscles ; 

 r.sem, receptaculum seminis ; sh.gl, shell-gland ; te, testes ; ut, uterus ; iito, uterine 

 pore ; vag, vagina ; vd, vasa deferentia ; yd, yolk-duct ; yg, yolk-glands (black) ; 

 6, male, 9, female genital aperture. (After Riehm.) 



stated to exist in the cuticle of Cestodes and Trematodes. If 

 true, this would tend to show that the parasitic mode of life of 

 these animals demands a complex nervous system comparable 

 with that of the Turbellaria, 



The reproductive organs, unlike the preceding systems, are 

 discontinuous from one proglottis to the next. The male and 

 female organs and their mutual connexions, especially in the 

 unsegmented Cestodes, may be compared in detail with those 

 of Trematodes, but the difference between the arrangement of the 

 generative organs of various Cestpdes. ig very great. 1 The penis 

 (Fig. 41, cs) is evaginated through the male pore (Fig. 41, <?), 

 and inserted far into the vagina ( ? , vag} of the same or another 



1 For example, the genitalia in Dipylidium caninum are duplicated in each 

 proglottis. Other differences are noted in the following table (pp. 89-90). 



