162 " ENTOZOA. 



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

 differences exist, wliicli 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 Van 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 from an examination of two 

 specimens which were much smaller than those from 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 refracting nucleus. They are 

 thought to possess a salivary function. According to the same 

 authority, there is also a separate, thin-walled, 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 solitary sac, it appears to be peculiar to 

 Fasciola hepatica, but Pagenstecher and Walter have described two 



* Without mentioning my name, MM. Paul Gervais and P. J. Yan Beneden 

 make the following strange statement in their "Zoologie Medicale," Tom. ii., p. 

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

 qui a ete decrit comme une autre espece, n'est aussi qu'un Distoma he2}aticum." 

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

 (" Die Menschlichcn Parasiten. Erster Band." Lief. 3, s. 530), which stands aa 

 follows : — " Das von Spencer Cohbold aus den Gallengangen de Giraffe beschriebene Dist. 

 fjiyanteum, das ich durch die Freundlichkeit seines Entdeckers in zwei Exemplaren 

 untersuchen konnte, istin der That eine eigene Species undkeineswegs, wie Van Beneden 

 angiebt, mit dam gemeincn Dist. hepaticum, identisch." 



