STRUCTURE AND DEVELOPMENT OF ECHINOCOCCUS 



35 1 



from a metamorphosis of scolices that have separated off from the brood 

 capsule. This takes place in the following way : Fluid accumulates 

 in the interior of the scolex, so that eventually nothing remains except 

 a sac consisting of cuticle lined by parenchyma. The cuticle gradually 

 thickens and several layers form (fig. 257). 



FlG. 255* Echinococcus hotninis in the liver. The fibrous capsule and 

 the wall of the echinococcus have been incised, so that the endogenous 

 daughter cysts may be seen. Reduced. (After Ostertag, from Thoma.) 



(3) Transformation of Brood Capsules into Daughter Cysts. This is 

 also held to be possible by various observers. New epithelial layers are 

 deposited between the cuticle 

 which lines the brood capsule 

 and the outer parenchymatous 

 layer. This parenchymatous 

 layer gradually disappears and a 

 newparenchymatous layerforms 

 in the interior from the paren- 

 chyma of the scolex or scolices. 

 Although it appears strange that 

 a completely formed scolex with 

 specifically differentiated tissues 

 and organs should retrogress 

 to more primitively organized 

 matter, and again become a 

 proliferating bladder, yet we can 

 hardly doubt that the older observations, regarding such a vesicular 

 metamorphosis, of Bremser (1819), v. Siebold (1837), Naunyn (1862), 

 Rasmusser (1866), Leuckart (1881), Alexinsky (1898), Riemann (1899), 

 Deve (1901), and Perroncito (1902) are correct. 



FIG. 256. Section through an echinococcus 

 scolex in process of vesicular metamorphosis, 

 twenty-six days after insertion in the pleural 

 cavity, x 250. (After Deve.) 



