THE PROLIFERATION OF ECHINOCOCCUS. 357 



bladder has often an irregular, more or less diverticular form. This is 

 particularly well seen in those worms which are found outside the 

 cranial cavity, and which are partly perhaps separate species. Some- 

 times their regular sinuses present an almost racemose appearance, 

 like the the so-called Cysticercus racemosus.* 



In the case of the familiar Echinococcus, which originates from the 

 Tcenia echinococcus living in the intestine of the dog, the state of affairs 

 is somewhat different. We shall afterwards have an opportunity of 

 studying these wonderful structures more closely, and will only now 

 summarise what is necessary in order to understand their relation to 

 other bladder-worms. 



Echinococcus is, like Ccenurus, polycephalous, but its heads differ 

 not only in their minute size and myriad numbers, but also in their 

 relations to the body of the bladder. For, instead of springing directly 

 from it, as has been hitherto the case, they originate on the wall of 

 special brood-capsules which lie in numbers on the inner wall of the 

 bladder. 



FIG. 204. Brood-capsule of Echinococcus, FIG. 205. Diagrammatic represen- 



with adherent heads in various stages of tation of a proliferating Echinococcus. 



development. ( x 36. ) 



The size of these brood-capsules never exceeds 1/5 to 2 mm. in 

 diameter, and even this size is attained only by the oldest capsules, 

 which enclose a dozen or more heads. At first the capsule contains 

 only a single head, but the number gradually increases, new heads 

 being continually budded off from the walls. The process of forma- 

 tion closely resembles that of the head of Cysticercus. A diverticulum 

 of the outer surface occurs, which grows out into a hollow caecum, 

 forming the tape-worm head, as in the ordinary bladder- worm. The 

 completed head then draws itself back into the cavity of the brood- 

 capsule, so that the suckers and hooks become ensheathed by the 

 former neck, and the originally club-shaped appendage now lies like a 

 berry on the inner wall of the capsule. Sometimes this invagination 



1 A striking instance of this has been lately described and figured by Megnin, Journ. 

 Anat. et PhysioL, PL vii., 1880. See also Bendz, "Om Oprindelsen af Dreiesygen hos 

 Faaret," Tidsskrlft for Landoekonomie, July 1857, a memoir which has remained to all 

 appearance unnoticed. 



