372 ON POLYCERCUS, 



Strongly dissents, and the history of the development, as above 

 described, shows that his conclusion was correct. Having, 

 however, only Meczuikoff's statements to rely upon, he was 

 necessarily led to some wrong deductions. Thus he describes the 

 caudal vesicle as invaginated in the '• blastogene," whereas, as we 

 have seen, the latter is really represented by a cellular mass from 

 which the Cysticercoids are developed by proliferation. His 

 detailed comparison with Ecliinococcus is rendered inaccurate in 

 several particulars by a similar cause; but in its main outlines 

 appears to us to present the true view of the case. " Le Cystique 

 du Lombric n'appartient pas au meme groupe que I'Echinocoque, 

 et il ne represente nullement dans son groupe le type de I'Echino- 

 coque. L'interessant parasite decouvert par MecznikofF est un 

 Cystique monocephale, monosomatique et polycerque. L'Echino- 

 coque, au contraire, est un Cystique polycephale, polysomatique 

 et monocerque. Les ressemblances sur lesquelles on s'est fond6 

 pour rattacher les deux formes a un seul et meme genre se 

 reduisent en definitive a de simples analogies qui ne portent pas 

 sur des parties homologues.""^ 



In the Cysticercoids hitherto described there are three main 

 types as regards the form of the completed larva: (1) those in 

 which there is a longer or shorter caudal appendage, containing a 

 small cavity, but in which no caudal bladder is present ; (2) those 

 in which such a caudal appendage is present and a caudal bladder 

 as well ; (3) those in which the caudal appendage is absent, but in 

 which there is a well-formed caudal bladder. 



Of the first group we have an example, it would appear from 

 Grassi and Rovelli's account, in the Cysticercoid of Taenia ellip- 

 tica. In T. 7nu7'ina, apparently, we have an example of the 

 second form, in which the opening of the investing caudal bladder 

 closes up ; while in Gysticercus tenehrionis, according to our 



* L.c. p. 34. It is to be remarked here that the description of Echino- 

 coccus as 'monocerque' is open to objection, the daughter-vesicles of that 

 genus being the equivalents of the caudal vesicles of other Cestodes. 



