234 THE ANIMAL PARASITES OF MAN 



usually a double crown of hooks, exceptionally the rostellum is transformed 

 into an apical sucker, the primitive armature of which then disappears. 

 The neck may be long or short. The young segments are broader than 

 they are long ; the fairly mature ones almost square ; the genital pores 

 project at the lateral borders, and alternate irregularly. Genitals single 

 in each segment. 



The testes are usually very numerous, and are situated in the lateral parts 

 of the central field ; the ovary, shell gland and vitellarium are situated in the 

 posterior half of the central field. The uterus has a median trunk with 

 lateral branches which develop later ; as these develop, the testes, and later 

 on the ovary and vitellarium, become atrophied. The egg-shell is thin and frail, 

 round, and with or without filaments ; the embryonal shell is thick with 

 radial stripes. There is a cysticercus, ccenurus or echinococcus stage which 

 is usually passed in. herbivorous animals ; the adult stage is passed in car- 

 nivorous animals and in man. 



i. Tcznia solium, L., p. p., 1767. 



Syn. : Tania cucurbitina, Pall., 1781 ; T. pellucida, Goeze, 1782 ; T. vulgaris, 

 Werner, 1782; T.^lentata, Gmel., 1790; Halysis solium, Zeder, 1800; T. 

 humana armata, Brera, 1802; T. (Cystotcenia] solium, Leuck., 1862, ; - 



The average length of the entire tapeworm is about 2 3 m., 

 but may be even more ; the head is globular, O'6 0*8 ro mm. in. 

 diameter. The rostellum is short with a double wreath of hooks, 

 22 32 in number, usually 26 28 ; large and small hooks alternate 

 regularly ; the length of the large hooks is 0*16 0-18 mm., of the 

 small ones o-ii 0*14 mm. The rostellum is sometimes pigmented. 

 The suckers are hemispherical, 0*4 0-5 mm. in diameter. The neck 

 is fairly thin and long (5 10 mm.). The proglottides, the num- 

 ber of which averages from 800 to 900, increase in size very 

 gradually ; at about i m. behind the head they are square and 

 have the generative organs fully developed. Segments sufficiently 

 mature for detachment measure 10 12 mm. in length by 5 6 

 mm. in breadth. The genital pores alternate fairly evenly at 

 the lateral border a little behind the middle of each segment. The 

 fully-developed uterus consists of a median trunk, with 7 10 lateral 

 branches at either side, some of which are again ramified. The eggs 

 are oval, the egg-shell very thin and delicate ; the embryonal shell 

 is thick, with radial stripes ; it is of a pale yellowish colour, 

 globular, and measures 0-031 0-036 in diameter ; the oncospheres, 

 with six hooks, are likewise globular, and measure 0*02 mm. in 

 diameter. 



