THE T.ENIA LATA OF BONNET. 413 



But an exact and detailed description of the worm was still 

 lacking. Only after the course of half a century was this want 

 apparently supplied by a treatise of the famous Genevan natural 

 philosopher Bonnet, " Sur le ver nomme' en latin Tsenia, en francos 

 Solitaire." * 



The description given by Bonnet in this work of the head of the 

 particular tape-worm, which he observed, agrees in all essential points 

 with that of Andry. It is true that he only succeeded in finding it 

 once with certainty, but in this case it appeared distinctly, just as 

 Andry described it, as a small black knob, which was placed on a 

 thin neck, and consisted chiefly of four plugs arranged in pairs and 

 with only one terminal opening. The surface (apex) lying between the 

 suctorial plugs, which, in the other tape- worms (as especially shown 

 by Tyson in the four from the cat) 2 is provided with circles of 

 hooks, in this case exhibited nothing but a shallow depression (un 

 enfoncement). 



But in spite of this conformity there was a great and striking 

 difference between the two descriptions ; for, from the structure of their 

 joints, Bonnet's tape- worms belonged, not to the first but to the second 

 species of Andry and Plater, or, in other words, they were not Tcenice, 

 but Bothriocephali. 



Since Bonnet made his worm the subject of thorough investigation, 

 and supplied the first really correct figure of it, at Geneva, where 

 Bothriocephalus was very frequent, and where he had abundant oppor- 

 tunity of observing the parasite, it was easy to suppose that the head 

 structure, first observed by Andry in the tape-worms, occurred in the 

 " Tcenici " ( = Bothriocephalus, Eud.) and also in the " Solium " (the 

 modern Tcenia saginata) assuming of course that the description of 

 Andry was based on no oversight or error. 



And indeed this supposition long obtained favour, and was not 

 refuted until thirty-seven years later. A mistake had, indeed, been 

 made not, however, by Andry but by Bonnet. The worm whose 

 head Bonnet described really represents a Tcenia saginata (Solium 

 of Andry), but the joints mentioned in connection with it originated 

 from the modem Bothriocephalus. 



Possibly the confusion arose from the circumstance that Bonnet, 



1 Mem. de Maihematique et de Physique pres. a VAcad. roy. Paris, t. i., p. 495, 1750. 



2 With the exception of the statements of Tyson and Andry, any account found in 

 ancient literature of the head-formation of the tape-worms is based on gross errors and 

 fantastic misrepresentations, which may here be omitted. I refer any one who is interested 

 in these to Tyson, " Lumbricus latus," Phil. Trans., vol. xii., No. 146, p. 124, 1683, 

 and to the compilation of Werner, "Vermium intest. br. exposit." tab. iv. : Lipsiae, 

 1782. Even in the year 1762 Linne* also flatly denies the existence of a head in the 

 tape- worms (" Amcenitates Acad.," tab. ii., p. 66). 



