232 T. B. ROSSETER ON HYMENOLEPIS FRAGILIS. 



The vesicula-seminalis (Fig. 3, V.S.) is a long sac 0*27 mm. 

 long with a mean width of 0*045 mm. Its narrowed distal end 

 terminates in a coiled efferent duct, which attaches itself in a 

 ligamentary form to the cirrus. It is early filled with sper- 

 matozoa from the testes, on the completion of which they (the 

 testes) become absorbed. The head of the spermatozoon (Fig. 12), 

 when fully developed and ready for transmission, is spatulate, 

 with a slight constriction in its centre. Its plastic contents 

 could not be differentiated, as they were unaffected by staining, 

 haematoxylin and safranine being the stains employed. 



The cirrus (Figs. 3, 5, 6) is a long, smooth, hollow rod. At 

 its distal end, where the vas-efferentia attaches itself, it tapers to a 

 fine point, with a circular orifice. The sheath of the cirrus (Fig. 5, 

 C.S.) is a continuation of the vasa-efferentia. At the distal end 

 of the cirrus, a short distance up, by the aid of a T \--in. objective 

 one finds that the sheath at its base or commencement is thrown 

 into a series of wrinkles or bands, as if to give it a firmer attach- 

 ment to the cirrus ; also that the cirrus is attached to the sheath 

 by very fine muscular fibres, evidently retractor muscles, because, 

 when the cirrus is retracted or at rest within its sheath, these 

 fibres hang loosely in a spiral form within the sheath. At its 

 proximal end the sheath becomes spinous or hispid. 



The cirrus-pouch (Fig. 5, C.P.) is a circular tube involuted more 

 or less at its proximal and distal ends, caused by the protrusion 

 or retraction of the cirrus-sheath, because when the cirrus is 

 everted for the purpose of coition the sheath is partially everted 

 with it, being, as is seen in Fig. 5, a telescopic arrangement. The 

 pouch does not run the whole length of the sheath, but is an 

 offshoot midway from the latter. 



Just below the male genital pore is the spinous bulb (Fig. 7), 

 which is characteristic of this species of tape- worm, and also of 

 T. sinuosa, the only two known Avian tape- worms whose cuticle 

 bears such an organ. 



The female genital organs call for but little comment. The 

 female genital pore (Fig. 1, Sec. 9) is situated posterior to the 

 male on the ventral side. The pore is an insignificant jagged cleft. 

 The vagina is cup-shaped ; the vaginal canal runs sinuously 

 obliquely to the anterior border of the segment in the median 

 line ; it then curves, runs proximally again for a short distance ; 

 again curves distally, and forms the receptaculum-seminis. 



