T. B. ROSSETER ON DREPAXIDOT-ENIA YENUSTA. 13 



the vasa efferentia can be traced between each of them and the 

 cirrus ; but there is no looping of the vas deferens, either on the 

 exterior or within the interior of the pouch ; and the pouch itself 

 is still a slender muscular sac. The length of the proglottides at 

 this stage has increased to 0-203 mm., and the width to 0*709 mm 

 Within the last twenty segments the sinus genitalis with the 

 vagina have made their appearance, and progressed in their 

 development ; although some fifty segments previously this had 

 been anticipated, as it is at this point that the invagination of the 

 cuticle of the segment takes place, and forms the rudimentary 

 concavity of the future sinus genitalis ; and this concavity is 

 never effaced, but persistently remains in the older segments 

 (Fig. 116). 



This in-pushing gradually continues, and thus the sinus is 

 evolved from the parenchymatous tissue; but there is as yet no 

 muscular thickening of the cuticle to form the genital papillse 

 until after the 300th segment is passed. Thirty segments farther 

 on the proglottides are sexually mature or complete, minus the 

 uterus. The testes have secreted their sperm, copulation has 

 taken place, the receptaculum seminis is filled with spermatozoa, 

 and the ovaries with their accessory glands occupy their normal 

 positions in the segments. At the 450th segment the uterus is 

 fully developed, and from the 563rd to the termination of the 

 strobila. the proglottides are complete uterine sacs for the further 

 development of the uterine eggs into the oncospheres or six-hooked 

 brood. 



The Genital Organs. 



The genital organs consist of male and female. 



The male organs are the testes, vas deferens, vesicula seminalis, 

 the cirrus pouch, and cirrus. 



The female organs comprise the vagina, receptaculum seminis, 

 ovaries, yelk-gland, shell-gland, and uterus. 



Each segment contains both sets of generative organs, and is 

 self -fertilising. The genital pore, with its papilla, is uniformly 

 unilateral. The male organs are always situated on the dorsal 

 side ; and the female organs, with the exception of the uterus, 

 which is dorsi- ventral, are situated on the ventral side. 



The Male Organs. — The testes are at first three globular bodies 

 (Fig. 10, a, a, a"), but when they ripen the proximal and distal 



