366 T. B. ROSSETER ON THE ANATOMY OF BICRAN0T2ENIA CORONULA. 



is everted and stained, they stand out prominently under a 

 -^Q mm. objective. Again, if the sheath is teased away from the 

 cirrus, the shreds still bear the spines ; neither is there any 

 caducity of these spines in the forming uterine segments ; they 

 only disappear, like the cirrus, by absorption. The sheath has 

 a diameter of 0'03 — 0*05 mm. I have formed the conclusion that 

 Dujardin mistook the spinous cirrus-sheath for the cirrus, and 

 looked upon it as an integral part of that organ. 



The excessive inflation of the vesicula seminalis inferior, or sac,. 

 with spermatozoa, causes great pressure to be brought to bear on 

 the longitudinal muscles of the cirrus pouch. This pressure drags 

 up the cirrus, and with it the sheath, causing them to extrude 

 and the cirrus to enter the vagina, whilst the resistance of the- 

 circular and oblique muscles contracts the sac, expelling the 

 spermatozoa through the tubular cirrus into the vaginal canal, 

 and thus filling the receptaculum seminis. After this the cirrus 

 and sheath return again within the pouch, but there are times 

 when both are left extruded from the genital cloaca. 



The measurements given above in connexion with the male 

 genital organs do not coincide with those given by Dujardin. This 

 is immaterial, for implicit confidence is not to be placed in the 

 use of the micrometer. In this case the free use I have made of 

 it has been unavoidable, but in all cases I have given the mean 

 of the many specimens of my own preparations, which I have 

 examined and described. 



Female Organs. 



If the description given by Dujardin of the male organs 

 is " terse," that of the female organs is more so ; and it is given 

 with such a reservation as almost to amount to a doubt. 



" Un deuxieme orifice situe au-dessous, arrondi et forme egale- 

 ment d'une membrane herissee de petites epines ; oeufs." 



This is all the description given by Dujardin of the female 

 organs of this tape -worm. 



The female organs consist of the vagina, with its canal ; the 

 vulva ; a receptaculum seminis, and fertilising canal ; a paired 

 ovary, and oviducts ; yelk and shell glands ; a uterine canal, and 

 uterus (Fig. 5 b). 



The vagina (Fig. 5 b m), with its canal and vulva, lies posterior 

 to the cirrus pouch, in the same plane with it, which is somewhat' 



