113 



duced by muscular fibres, extends from the circlet of books through 

 the anterior portion, becoming spread out and lost in the posterior. 



The hooks (fig. 3) were about ,-5-0 th of an inch in diameter. Their 

 outer half was formed by a strong, curved, conical claw, the inner half 

 by a somewhat crooked process with a blunt end. From the posterior 

 surface of the junction of these two portions a strong rounded spur 

 passed backwards and gave the hook additional firmness in its place. 

 The hook contained a cavity, a process of which passed into each of 

 its portions. Altogether it was not unlike the thickened liber-cell of 

 of a plant. 



Behind the circlet of hooks, the shape of a transverse section of the 

 body is quadrilateral, and at each of the four corners a large rounded 

 disc with a more or less flat surface is to be seen, — the sucker. In 

 structure, when unaltered, the suckers appear to be homogeneous, 

 with granules and two or three of the peculiar corpuscles to be de- 

 scribed immediately, imbedded in their substance. Under the action 

 of acetic acid, however, a radiated fibrillation frequently became 

 visible. 



Scattered through the substance of the Echinococcus, and giving 

 it a very peculiar dotted appearance under a low power, a number of 

 oval, strongly refracting corpuscles may be observed. They are very 

 uniform in size, and have a long diameter of about stW*^ °f ^^ 

 inch. They are what have been called the calcareous corpuscles of 

 the Echinococcus ; — inasmuch, as in the Cysticerci and other cystic 

 worms they have been observed to be converted into carbonate of 

 lime ; but I believe that this is entirely a result of that peculiar de- 

 generation to which the cystic Entozoa are so liable, and that, in the 

 young and normal adult state, these peculiar corpuscles (which are 

 found in all the Cestoidea and Cystica) are never calcareous, but are 

 composed of an albuminous substance. 



The mistake has arisen, I think, from two causes. In the first 

 place, in old cystic worms these corpuscles are frequently converted into 

 a calcareous substance, although they retain their transparency and 

 strongly refracting powers ; and secondly, because when acid is added 

 to a number of Echinococci, gas is very commonly developed from 

 calcareous substances contained either in them or in the fluid in which 

 they swim ; at the same time the action of the acid rapidly causes 

 the corpuscles to become clear vesicles, so that nothing seems more 

 natural than to connect the one circumstance with the other. 



Having paid great attention to the process, however, I can 

 decidedly affirm — 



1 . That acetic acid dissolves ovit the contents of the corpuscles in 

 young and fresh Echinococci, without the least evolution of gas from 

 them ; and that the same assertion holds good of the corresponding 

 corpuscles contained in the spirit specimens of Taenia and Bothrio- 

 cephalus which I have examined. 



2. That caustic ammonia produces little cavities and sometimes a 

 concentric lamination in these bodies. 



And, 3rdly, that in a spirit specimen of an Echinococcus from the 

 No. CCXLV. — Proceedings of the Zoological Society. 



