T^NIA ECHINOCOCCTJS, 265 



its very earliest stage — after a short while displays in its interior 

 a vacuole-hke cavity, the latter being occupied, however, with 

 a clear hmpid fluid. Its margins become more and more 

 clearly defined until the cavity is by and by seen to be lined with 

 a distinct cuticular membrane. The papilla increasing in size, 

 becomes at first elongated or oval, eventually scoleciform, or even, 

 perhaps, a true echinococcus head. Thus far, the description 

 bears out, in a measure, the theoretical notions entertained by the 

 older authors ; but the developmental process does not stop here, 

 and it is even a question if, in any case, it ever does so. The scolex- 

 Kke development has now — possibly, it may be, not in every case 

 — has now, I repeat, to sacrifice itself by developing in its interior 

 a brood of scohces or echinococcus heads. In other words, it 

 becomes gradually transformed into the so-caUed brood-capsules 

 of Leuckart and other authors.* All observers who have micro- 

 scopically examined fresh echinococci must have seen these 

 capsules. Portions of the essential vital endocyst, here forming 

 the outer wall of the brood-capsule, now thicken in the same way 

 that the original maternal endocyst had done, and these thickened 

 portions, in their turn, become true scolices, or, in some cases, 

 scolicecoid formations. By a process of inversion — precisely 

 similar to that which has been so often described and figured in 

 the case of Coenurus — the heads are withdrawn, as it were, into 



* I adopt the term " brood-capsule" as eminently convenierLt and expressive ; but I 

 may observe that these sacs were well known to WUson and Busk. The former spoke 

 of the capsule as "a delicately thin proper membrane, by which the Echinococci are con- 

 nected with the internal membrane of the acephaloeyst" (Med.-Chir. Trans., 1845, Vol. 

 xxviii., p. 21). Mr. Busk described the Echinococcus heads as " attached to a common 

 central mass by short pedicles, which appear to be composed of a substance more 

 coarsely granular, by far, than that of which the laminae of the cyst are formed. This 

 granular matter is prolonged beyond the mass of Echinococci into a short pedicle 

 common to the whole, and by which the granulation is attached to the interior of the 

 hydatid cyst." What Mr. Busk here describes as a granulation, can only be equivalent 

 to the brood-capsule and its entire contents, but he elsewhere speaks of the capsule itself 

 as a " dehcate membranous envelope." It should be borne in mind that Mr. Busk's 

 paper was communicated to the Microscopical Society so early as the 13th of Nov., 1844; 

 being pubUshed in the Transactions for that year. The original series of this periodical 

 is now very scarce. — T. S. C 



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