ON THE ANATOMY OF THE ECHINOCOCCUS VETERINORUM 215 



I have here endeavoured to notice all those Memoirs which, at the 

 time of their publication, made a definite addition to what was already 

 known upon the structure of EcJiinococciis. The literature of the 

 subject is somewhat voluminous, and hence the necessity of this 

 limitation, and the consequent absence of any account of the valuable 

 memoirs of Goodsir, Curling, Busk, and Erasmus Wilson, all of whom 

 had been anticipated by the continental observers. 



DESCRIPTION OF THE PLATES. 



PL. XXVIII. [Plate 21]. 



"Fig. I. A single detached Echinococcus-head, with the hoolis and suckers protruded. 

 The position of the si.x observed cilia is indicated by the wavy lines. 



Fig. 2. A fragment of the Endocyst, with one of the abortive hooks. 



Fig. 3. Fully formed hooks from an Echinococcus-head, seen in profile and in front. 



Fig. 4. Secondary cyst still attached to the wall of the primary. The external Echino- 

 cocci are seen in various stages of extension and contraction ; the internal Echinococci shine 

 through the walls of the cyst. 



Fig. 5. A similar cyst, with only one external Echinococcus. The relation of the Endocyst 

 to the laminated Ectocyst is well seen, and the budding Echinococci on the inner surface of 

 the former, which will eventually become external heads of secondary cysts. 



PL. XXIX. [Plate 22]. 



Fig. 6. A very small secondary cyst, with the remains of its pedicle above, and of an 

 external Echinococcus below. 



Fig. 7. Secondary cyst burst at the upper part and allowing three of the internal Echino- 

 cocci to escape. The contrast of their appearance with the two dark and withered external 

 Echinococci is well-marked. 



Fig. 8. Portion of the wall of a secondary cyst, showing the ramified vessels, and the 

 attachment of the internal Echinococci to its interior surface. 



Fig. 9. A large secondary cyst with no external head, but with the remains of its 

 pedicle appearing as a brownish spot. 



Diagrams : — Hypothetical representations of— A. a young Tmnia ; B. a Cccnunis ; C. a 

 Cysticercus ; D. the same, encysted ; E. a Cysticercus, encysted, enlarged, and developing 

 many heads (like Ctcntirus) from the upper portion of its outer (now inner) surface ; E. a 

 similar form, which developes heads from the lower portion of its outer (now wholly outer) 

 surface, and so becomes an Echmococais-zyA. 



