226 THE ANIMAL PARASITES OF MAN 



number. Genital pores marginal, on left side ; the female surface ventral. 

 Testes few, generally three in each segment one left and two right of the 

 median line. Eggs with three separate shells ; inner shell with a small 

 knot at each pole. The larva a Crytocystis or Staphylocystis. Intermediate 

 host insect or myriapod. Weinland proposed this with Tcenia ftauopunctata 

 as type, which is the same as diminuta. 



Genus Drepanidotcenia, Railliet, 1892. 



Head provided with a single row of uniform hooks, few (8 to 20) in 

 number, with dorsal root much longer than ventral root, the latter always 

 small, with prong directed posteriorly when the rostellum contracts. Larval 

 stage found in small crustaceans. 



The two genera thus differ in having the dorsal root of the 

 hooks much longer than the ventral or prong in Drepanidotcenia, 

 and the hooks few in number ; the hooks are similarly formed in 

 Hymenolepis, but when present vary from 24 to 30. 



A third genus is closely related, Dicranotcznia, Railliet, 1892, 

 which has the dorsal root of hooks shorter than the ventral root 

 or prong. The two latter only are known in birds. F. V. T.] 



I. Hymenolepis nana (v. Sieb.), 1852. 



Syn. : Tcenia nana, v. Sieb., 1852 (nee van Beneden, 1867); T. cegyptiaca, 

 Bilh., 1852 ; Diplacanthus nanus, Weinld., 1858 ; T. (Hymenolepis) nana, Lckt., 

 1863. 



The worm is 10 15 mm. in length and 0*5 0*7 mm. in breadth ; 

 the head is globular, 0*25 0*30 mm. in diameter. The rostellum 

 has a simple crown consisting of twenty-four or twenty-eight to 

 thirty hooks, which are only 0*014 0*0 18 mm. in length. The neck 

 is moderately long ; the proglottides are very narrow, about 150 

 in number, 0*4 0*9 mm. in breadth, and 0*014 0*030 mm. in length. 

 The eggs are globular or oval, 0*030 0*037 0*048 mm. ; the onco- 

 spheres measure 0*016 0*019 mm. in diameter. 



This species was discovered by Bilharz in Cairo, in 1851 ; it 

 was found by him in great numbers in the intestine of a boy 

 who had died of meningitis. For several years this was the only 

 case, until 1885, since when numerous cases have come to light. 

 Spooner, 1873, even reported a case from North America, which 

 may, however, have related to Hymenolepis diminuta. In Europe 

 the worm is particularly frequent in Sicily, but it has also been 

 repeatedly observed in North Italy ; it has, moreover, been 



