Zoological Society. 381 



oval portion, notched at the extremity : attached to the posterior sec- 

 tion, and, as it were, sunk in the notch, there is a small appendage 

 of variable form, which usually appears to be clear and somewhat oval, 

 or pyriform, with an irregular ragged extremity. 



The body of the Echinococcus consists of a very clear transparent 

 substance, slightly granular or dotted internally, and limited exter- 

 nally by a well-marked structureless layer. Forming a circle round 

 the conical anterior extremity there are from twenty to thirty strong 

 hooks, which sometimes appeared to be in a single, sometimes in a 

 double row. In the latter case the hooks of the upper row alternated 

 with those of the lower. A delicate longitudinal striation, as if pro- 

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

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



The hooks were about y-jyoth 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 

 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 2yVo tn 0I an 

 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, because in old cystic worms these corpuscles are frequently con- 

 verted into a calcareous substance, although they retain their transpa- 

 rency 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. 



