NUMBER AND DISTRIBUTION OF THE SPECIES. 405 



rants the union of the two species, though this has been frequently 

 proposed by certain helmiuthologists.^ 



The number of species of tape-worm belonging to this 

 group is, as far as we yet know, at most a dozen and a half. 

 Of course we are as yet hardly acquainted with any but 

 European species, and these but imperfectly,sothatin course 

 of time the number will probably be much increased.^ 

 With the exception of the Tmnia solium, e Cyst, cellulosce 

 and the T. saginata e Cyst, bovis, they are all found in 

 Carnivora ; in the cat, T. crassicollis e Cyst, fasciolan ; 

 in the dog, T.serrata e Gyst.pisiformi, T.marginatae Cyst. 

 tenuicoUi, T. Krabbei e Cyst, tarandi, T. ccenurus e Co&nuro 

 cereirali; in the fox, T. crassiceps e Cyst, longicolli,^ T. 

 polyacantha e Cyst. sp. ; in the polecat, T. intermedia, T. 

 tenuicoUis e Cyst, talpce, &c. 



The size of tape-worm body differs widely in the 



individual species, but is on the whole very considerable. 



The hooks also are always large and strong, except in a ^^o- 236.— 

 I. • ^ ji 11 m , ■ n- 1-11 Cystwercus 



few species, such as the small 1. tenuicottzs, and indeed fasoiolaris 



few other Tcenice can equal these forms in this respect. f''^*- ^"^l- 



The anterior root of the smaller hooks is broadened at the end and 



notched like an inverted heart. 



In spite of much structural resemblance, the different species are 



not hard to distinguish from one another. It is true that one of our 



most famous helminthologists^v. Siebold — affirmed the opposite only 



a few decades ago, and declared emphatically that the Tcenia solium 



of man was identical with the above-mentioned tape-worms of the 



dog, and also with T. crassiceps and T. intermedia. This has, however, 



been sufficiently disproved by Kiichenmeister and by myself. Even 



, if we regard the differences in size and habit as irrelevant in spite of 



their constancy, and due, as v. Siebold would have it, to the differences 



in the hosts inhabited, there are yet other weighty and distinctive 



' Zeder unites these two to form the genus Polycephaltis. 



" In the liver o£ Arctomys Lvdomciana I observedjust lately the Cysticercus of a hitherto 

 unknown Tcenia, with twenty-four extremely small hooks. Moniez has also enriched 

 our knowledge of the bladder-worms by the discovery of a new species, Cysticercus Krabbei. 

 It lives in the muscles of the reindeer, and is developed in the dog to a segmented chain 

 (toe. cit., p. 44). 



' The doubt which Moniez casts [loc. cit., p. 69) on the relationship between Cysticercus 

 longieoUis and T. crassiceps is quite gratuitous. I have associated the two forms not only 

 because of the hooks, but because I have produced the Tcenia in question from the Cysti- 

 cercus. It is impossible to confuse the latter with the Cysticercus taZpce (which, though 

 bookless, according to Rudolphi, is in reality provided with small hooks), although both 

 species occur both in the mole and in the field-mouse, and although the former also has 

 Bometunes been designated Cysticercus taZpce. It is equally impossible to regard 

 Cysticercus longicollis with Pffifff^^^ t^ycMfgiOi^fylf^ fasoiolaris. 



