? 



160 T. B. ROSSETER ON HYMENOLEPIS UPSILON. 



mation of a new genus, as the hermaphroditic arrangement of 

 the generative organs are known to present great variations : 

 neither do I look upon it as an abnormality, but I rather 

 favour the possibility of its being a reversion in this instance 

 to an original form. 



Description of Plate 6. 



Fig. 1. The entire worm, x 35. 

 ,, 2. The scolex with rostellum retracted x 70. 

 3a. The scolex under pressure, to show suckers ; also 



rostellum with bulb, minus the hooks x 70. 

 ,, 3b. Longitudinal and circular muscles of the rostellum, 

 diagrammatic. 



4. Hooks from the rostellum. a-c, Pfaff and Olrik's 

 specimens ; d, Krabbe's specimen x 920 (after 

 Krabbe) ; e, from Hymenolejns upsilon x 700. 



5. The last seven segments in the strobila to show evolu- 

 tion of the genitalia. For references see Fig. 8. 



6a. Embryonic egg from terminal segment. 



,, 66. From uterine sac of free proglottis x 350. 



7, V-shaped uterine sac from free segment x 35. 



.,, 8. Isolated male and female organs, diagrammatic. (^ : c, 

 cirrus ; c s, cirrus sheath ; h v, heart-shaped vesicle, 

 possibly expulsion vesicle ; c ^j, cirrus pouch ; v s i, 

 vesicula seminalis interior ; v d, vas deferens ; v s ex, 

 vesicular seminalis exterior; v e, vas efferens; t t t, 

 the three testes. 



$ : V 2^, vaginal pore ; v, vagina ; v c, vaginal canal ; 

 r s, receptaculum seminis ; o o, ovaries ; s g, shell- 

 gland ; y g, yolk-gland. 



,, 9. See note p. 158. 



7) 



J5 



Journ. Quekett Microscopical Club, Ser. 2, Vol, XL, No, C8, April 1911. 



