T. B. ROSSETER ON HYMENOLEPIS FRAGILIS. 231 



Dr. v. Linstow, to whom I am indebted for much kindness, in 

 his work on Taenia ursina, n. sp., taken from the Brown Bear 

 ( Ursus arctos), Taenia davainae struthionis Houttoyn (camel), and 

 Taenia serpentulous Schranck, from Corvits corona (Archiv fur 

 mikroscop. Anatomie, Band 42), in all three instances felt com- 

 pelled, in describing the male genital organs, to depart from the 

 beaten track, and to call the sac which under different circum- 

 stances would have been the cirrus-pouch, the expulsion-blase, 

 because the bladder itself was distinct from the cirrus. Although 

 the cirrus, with the coiled vas-deferens and prostate gland, lies 

 within the " expulsion-blase," yet in neither species did the " ex- 

 pulsion-blase " contain, nor, according to the researches of von 

 Linstow, did the cestode itself possess a vesicula-seminalis, the 

 coiled vasdeferens fulfilling the function of the organ. 



In the case of H.fragilis it is so different, because the creature 

 possesses a seminal vesicle with a coiled vasa-efferentia, and the 

 cirrus, with its sheath and pouch, is totally distinct from and 

 independent of the bursa, and this latter does not fulfil the 

 functions of a contractile " expulsion-blase " or bladder ; neither, 

 as far as my observations lead me to a conclusion, does the 

 cirrus-pouch in this instance fulfil such an office, as it is inde- 

 pendent of the seminal vesicle ; but the latter organ, having 

 been filled to repletion with spermatozoa from the testes, pressure 

 is brought to bear through the swollen coiled efferent ducts, 

 forcing up the funnel-shaped base of the cirrus, and consequently 

 the sheath to which the elevator-muscles at the anterior or 

 invaginated end of the pouch are attached. This causes the 

 cirrus to protrude, the coiled vasa-efferentia to lengthen itself 

 out, the sperm to flow up through the ducts of the cirrus 

 coition ensues, and a prolapsus of the vesicle naturally follows. 



The prostate gland (Fig. 4) is claviform. It is covered dorsally, 

 proximally, and partially distally by the vesicula-seminalis. At 

 its proximal end it bifurcates, each duct of the bifurcation 

 elongating and attaching itself to the proximal end of the 

 cirrus-sheath. 



The vas-deferens interior (Fig. 3, Y.D.I.) enters the bursa 

 at its distal end, runs upwards nearly the whole length of the 

 bursa ; its proximal end dilates into the form of a reservoir 

 (Fig. 3, R) ; it then curves, and, descending, forms the vesicula- 

 seminalis. 



