14 T. B. ROSSETER OX DREPANIDOT.ENIA YENUSTA. 



testes change to an oval form ; the central one is situated in the 

 posterior-median line, and is, from its " Anlage " up to its final dis- 

 appearance, stationary. It is only in the young segments that their 

 structure can be studied with any degree of accuracy. They are 

 then seen to be composed of a number of pyriform glands (Fig. 2), 

 which are filled with small globular nucleated cells, with their 

 ducts directed towards the centre of the gonad. At the side of 

 each gonad, where the efferent duct makes its exit, is a depression 

 or cavity. The sperm secreted by the testes, in its initial stage 

 as seen in sections, is a light grey flocculent substance, rolled up 

 in coils. These minute coils are, on examination with a high 

 power, seen to be immature spermatozoa ; what change they 

 undergo, either in the testes or in their passage along the ductus 

 efferens to the vas deferens, I do not know ; but the looped 

 vas deferens within the cirrus pouch is always filled with mature 

 s23ermatozoa, ready to be passed on by the cirrus into the vagina. 

 The spermatozoon, as seen in the receptaculum, is a long thin 

 filament with a diameter of 1/x. I have searched in vain to find 

 the head of an individual. Even when the ovaries have exhausted 

 themselves and, together with the yelk and shell-gland, have 

 disappeared, the residue of the spermatozoa within the recep- 

 taculum still tenaciously remains, but both ultimately become 

 absorbed in the tissue. 



In ripe segments the oval proximal and distal testes measure 

 0*118 by 0084 mm. ; the diameter of the median testis is 

 0*135 mm. As I have remarked above, when the male organs- 

 develop these two testes separate themselves from the median 

 one, and take up a position, the one nearer the proximal, and the 

 other nearer the distal margin, or side of the proglottis. As 

 they separate the vas efferens, Fig. 10, h, h\ h", elongates itself by 

 cellular growth. Taking the distal testis, we find the duct 

 springs from the farther side of the gonad, courses over it, hangs 

 somewhat loosely, and then attaches itself to the efferent duct 

 of the median testis ; and in like manner to the efferent duct 

 of the proximal testis. As it ascends to the cirrus pouch this 

 duct becomes the vas deferens ; and previous to entering the 

 pouch, which it does on the ventral side, it forms itself into three 

 loops (Fig. 10, c). It is only in young segments that this duct can 

 be definitely traced, as in the ripe segments it is either obscured 

 by the density of the tissue, or else by the developing uterus. 



