162 BNTOZOA. 



or near the centre of the termination of the tail. Many other minor 

 differences exist, which it is unnecessary to insist upon, especially 

 as they are, in the main, dependent upon those already referred to ; 

 but sufficient has, I think, been advanced to show that the notion 

 entertained by Yan Beneden, namely, that these two forms are 

 specifically identical, is incorrect. In this view, I am glad to find 

 I have the support of so discriminating an authority as Leuckart, 

 who arrived at the same conclusion fi?om an examination of two 

 specimens which were much smaller than those fi'om which the 

 figures in the frontispiece have been taken.* 



Special Structures. — Before passing to the consideration of the 

 development of the common fluke, I may refer to one or two other 

 structural pecuharities which I have hitherto omitted to mention. 

 In addition to the cutaneous system of glands, Leuckart mentions 

 the occurrence of a few equally distinct isolated gland-elements in 

 the neighbourhood of the pharynx, as well as others imbedded be- 

 tween the muscles of the pharynx and also between the muscles of 

 the oral sucker. The cells are filled with coarsely-granular con- 

 tents, and also display a highly refi:"acting nucleus. They are 

 thought to possess a salivary function. According to the same 

 authority, there is also a separate, thin-waUed, muscular sac, form- 

 ing a distinct and independent organ, though intimately connected 

 with the true pharynx. It appears to be a sort of diverticulum, 

 for Leuckart has occasionally seen it filled with the ordinary intes- 

 tinal contents. As a sohtary sac, it appears to be pecuhar to 

 Fasciola hepatica, but Pagenstecher and Walter have described two 



* Without mentioning my name, MM. Panl Gervais and P. J. Van Beneden 

 make tlie foUowing strange statement in their "Zoologie Medicale," Tom. ii., p. 

 201, Paris, 1858): — "Le Distome trouvS, en Europe, dans le foie d'une Girafe, et 

 qui a ete decrit oomme une autre espece, n'est aussi qu'un Distoma hepatieum." 

 As a " set off" against this, it is only due to myself to add Leuckart's comment 

 (" Die Mensohlichen Parasiten. Erster Band." Lief. 3, s. 630), which stands .as 

 follows : — " Das von Spencer Cobbold aus den GaUengangen de Giraffe beschriebene Dist. 

 giganteum, das ich duroh die Freundliohkeit seines Entdeckers in zwei Bxemplaren 

 untersuchen konnte, ist in der That eine eigene Species und keineswegs, wie Van Beneden 

 angiebt, mit dem gem.eiiien Dist. hepatieum identisch." 



