156 PEACTICAL PARASITOLOGY 



serialis ; and " Echinococcus " of T. echinococcus. The Coenurus 

 forms many scoleces, while the Echinococcus forms brood-capsules 

 and daughter-bladders, and from these many scoleces are formed. 1 



Herbiverous mammals harbour representatives of another group of 

 Tseniidee, the Anoplocephales. The most interesting are those of the 

 horse, which are characterized by very short overlapping segments. 

 They are Anoplocephala plicata (Zed.), A. perfoliata (Gze.), and 

 A. mamillana (Mehl.). The species are distinguished by peculiarities 

 in the structure of the head, which is invariably bookless. In 

 A. mamillana, a worm of about 5 cm. in length, the head is small 

 and is furnished with lateral elliptical suckers. In the other two 

 species, on the contrary, the head is large and the suckers are placed 

 upon its summit. The variety most commonly met with is A. per- 



FIG. 77. Anoplocephala perfoliata. FIG. 78. Head of Anoplocephala 



(Gze.). Natural size. (After Railliet.) plicata (Zed.). 10 : 1. (After Railliet.) 



foliata. This worm attains a length of 8 cm., and is characterized by 

 four lobes, directed backwards, upon the head. In A. plicata, which 

 grows as long as 80 cm., these appendages are absent. Owing to the 

 length of the dorso-ventral diameter, the proglottides are difficult of 

 examination. It is certain, however, that the formation of the genital 

 organs begins in the segments next to the head, and is soon com- 

 pleted; that the genital openings are all situated upon the same 

 margin ; and that the genitals are arranged transversely of the pro- 



1 The bladder- worm of T. crassicollis (Cyst, fasciolaris) is found in the liver of 

 rats and mice ; that of T. serrata (Cyst, pisiformis] in the liver of hares ; that of T. 

 marginata (Cyst, tenuicollis] in the omentum of sheep ; that of T. krabbei in the 

 muscular structure of Tarandue rangifer ; and Ccenurus cerebralis, the Cysticercoid 

 stage of T. coenurus, is found in the brain of sheep, where it gives rise to the disease 

 known as " gid." Coenurus serialis, the bladder-worm of T. serialis, is found in hares 

 and rabbits. The occurrence of Echinococcus has already been given above. 



