T. B. ROSSETER ON DREPANIDOT.^NIA VEXUSTA. 19 



means the ova become fertilised, and are passed on into the uterus 

 by the uterine canal. 



The uterine canal (Fig. 10, ])) springs directly from the shell 

 gland, and runs transversely through the median dorsi-ventral 

 line of the proglottis. As it approaches the proximal margin of 

 the segment it slightly undulates, trending towards the anterior 

 of the segment but afterwards continues its original course. It 

 is a blind canal, having no exit pore, and its diameter is 0*020 mm. 

 The uterus (Fig. 11) is a simple one — that is, the canal has no 

 tubules ; but the uterus is formed by the budding-off on either 

 side of sacs, or pouches, for the reception of the fertilised eggs 

 as they are passed on through the canal. These pouches ramify 

 among the tissues, ranging themselves on either side of the 

 segment, until it becomes a swollen uterine sac. Here the eggs 

 mature and develop into the oncospheres or six-hooked brood, and 

 hke the ova of other Tseniae whose uterus is destitute of a pore, 

 they have to await the desiccation of the proglottis or the inges- 

 tion of it by an invertebrate, before being set free. 



The mature eggs have no appendages. They have two 

 membranes, an outer covering or shell (?) and a secondary or 

 vitelline membrane. The clear space between the shell and the 

 second membrane contains a quantity of fat globules. As 

 development progresses these fat globules are absorbed, and one of 

 two things occurs in connexion with this secondary membrane : 

 either it becomes absorbed, or it adheres to and forms an 

 endothelial lining to the shell. If the latter, it remains so, for in 

 the latter stages of development the embryo lies perfectly naked 

 within the egg. It is not my purpose to discuss the successive 

 stages in the metamorphosis of the embryo from the morula 

 stage to the development of the oncosphere, as these have been 

 almost exhaustively dealt with by Van Beneden and Moniez in 

 connexion with the ova of mammalian Cestodes; but I must 

 make a few observations on a stage in the development of the 

 embryos oi Dre2). I'emtsta, Budolf Leuckart tersely says : "The 

 young Cestode embryos have not the least resemblance to the 

 adult form ; they are microscopic balls with six apical hooks, and 

 differ widely from the tapeworm both in shape and size. Between 

 these two extremes we find a long series of wonderful meta- 

 morphoses." I have, in a previous communication, explained that 

 portion of the development of this Taenia by which the cysticercus 



