DR. THEODOK NEUMANN. 243 



The eggs with the embryos therein are transported into 

 the stomach of some intermediate host, usually some 

 herbivorous or omnivorous animal ; there the young 

 worms leave the eggs and begin at once to work a path 

 through the walls of the intestine, especially by means 

 of the hooks mentioned. Sooner or later they reach a 

 blood-vessel, and may thus be carried to the remotest 

 parts of the body until they finally settle in some defi- 

 nite organ. Here they lose their embryonal hooks, which 

 may often be found in the surrounding tissues a long 

 time after, and change into thin or thicU-skinned blad- 

 ders filled with water, which do not betray their animal 

 nature in any way, save by some slow, wave-like contrac- 

 tions. These bladders grow, however, and become at 

 last a rather considerable object, around which the tissues 

 of the host have secreted a cover of connective tissue — a 

 cyst. At the same time we notice on closer inspection 

 that the wall of tliPe bladder begins to thicken in one 

 place ; this thickening increases and protrudes into the 

 interior as a hollow projection, which grows in length 

 and finally, as it does not find sufficient room inside, 

 folds itself into many wrinkles and curves. The walls 

 become also thicker and exhibit soon at the bottom of 

 the depression some growths which prove to be four 

 sucking cups inverted, and sometime a rostellum with a 

 circle of hooks. All this lies yet in the interior of the 

 bladder like the finger of a glove turned inside out ; 

 soon, however, this formation does turn out, so that the 

 inner wall of the growth becomes the outer, whereupon 

 the whole represents a well developed scolex of the tai)e- 

 worm with sucking cups and hooks. 



The bladder is called cysticercus. For a long time it 

 was considered an itidependent animal; only recently its 

 relations to the grown- up form of the tape- worm have 

 been established. Formerly they were considered as 

 water-bags, degenerated parts of the animal body, and 



181 



