COLONIAL OYSTICERCOIDS. 367 



Ccenurus-hlaMev, and, like these, is undoubtedly to be referred to 

 the six-hooked embryo. The first developmental stage observed by 

 Mecznikoff appeared to be a sohd ball of about 0'08 mm., with an 

 unusually thick cuticular envelope and cellular contents. The latter 

 subsequently become clear on attaining a diameter of 0'14 mm., when 

 the embryo lies upon the inner surface in the form of a cellular layer. 

 Soon the buds begin to form, and that exclusively from the cellular wall, 

 which becomes thicker at certain spots, and sends little projections (A) 

 into the inner cavity. Although at first flat, and connected by their 

 broad bases with the cellular wall, the protuberances, as they grow 

 larger, gradually detach themselves from the subjacent layer. This 

 separation is facilitated by the development of a hollow space in the 

 interior of the basal portion, ^ so that after a time the bud is only con- 

 nected with the mother-bladder by a thin filament (S). Finally, this 

 connection is destroyed, and the bud thus becomes an oval body lying 

 freely in the interior. It then proceeds to undergo its further develop- 

 ment. This is essentially the same as that which we have already 

 served in the buds situated inside the brood-capsule in the Echino- 

 cocci, only that in this case not only head and neck are formed, but a 

 third joint, consisting of a kind of caudal bladder. All these parts 

 are formed almost simultaneously, for the originally compressed and 

 solid bud increases in length, then becomes hollow inside, and 

 becomes jointed by the development of the hook-apparatus in front 

 and a bladder-like expansion behind. When the suckers and hooks^ 

 are completely developed (B), the anterior part of tlie body draws 

 back into the caudal bladder by invagination of the neck, so that at 

 the end of its development the worm has exactly the same position 

 as we formerly observed in Cysticercus arionis. 



The short description which we have given of this wonderful 

 Tcenia form by no means exhausts the similarities which sometimes 

 exist between the Cystercoids and the Uchinococci. The former are 

 not only capable of internal proliferation, but in some cases multiply 

 also by external buds. 



Villot observed this process in the already mentioned Cysticercoids 

 of Glomeris, where it was so often repeated, that the parasites assumed 

 quite a racemose appearance, from which fact, indeed, he has named 

 these forms " Staphylocysts." In this form they may be seen hanging 

 together in dozens (Kg. 214, A) in the ureter of their host. Such a 

 colony contains larger and smaller, younger and older bladder-worms, 



' Mecznikoff inaptly compares this hollow space to the interior of a brood-capsule. 



' Although the rudimentary hooks are in a double row, the definitive hook- apparatus 

 consists only of a single circle, for the rudiments of the second circle become abortive, and 

 disappear. 



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