CESTODA 



119 



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 " delicate membranous envelope." It should be 

 borne in mind that Busk's paper was communicated to the 

 Microscopical Society so early as the 13th Nov., 1844; being 

 published in the ' Transactions ' for that year. 



In the completely developed state the echinococcus-heads 

 exhibit somewhat variable characters as to size and form, the 

 latter differences being, for the most part, dependent upon their 

 degree of contraction and vitality. In the perfect condition 

 they vary from the ^" to the 

 " in diameter, being usu- 

 ally about the ^" '. They are 

 solid, and when stretched out 

 exhibit an hour-glass-like 

 constriction at the centre of 

 the body, which divides the 

 scolex into an anterior part 

 supporting the rostellum and 

 suckers, and. a posterior 

 part which has been com- 

 pared to the caudal vesi- 

 cle of ordinary Cysticerci. 

 The rostellum supports a 

 double crown of hooks, but 

 the disparity of the two series 

 is scarcely sufficiently marked 

 to render their distinction ob- 

 vious. The hooks of the 

 smaller row vary in size from 



ToVo 



" 



an 



whilst 

 those of the larger series are 



from ^/' to 



333 



In all in- 



FIG .S3. Separate scolex, or echinococcus-head. 

 Magnified 500 diameters. After Huxley. 



stances the root-processes are incompletely developed, and con- 

 sequently vary in thickness. They are, as Leuckart also has 

 stated, apt to exhibit abnormalities. 



In regard to the development of the echinococcus-heads it 

 further remains for me to observe that a distinct water- 

 vascular system is recognisable in the scolices. 

 intervention of the pedicle of the scolex this sys 

 connected with the brood- capsule, and also with the 



