132 



ENTOZOA. 



drawn the liooks with the points downwards.* On referring to 

 the edition of Cuvier's work, edited by his pupils, I find Blan- 

 chard's figure to indicate an arrangement of the hooks precisely 

 such as I have myself seen and figured, with the aid of a camera, 

 more than once;t in these cases the cusps were directed forwards. 

 It can scarcely be doubted, therefore, that under different circum- 

 stances, the same animal may display the hooks in either direction, 

 most probably by inverting and everting the head ; the performance 

 of this function having hitherto, perhaps, escaped observation. In 

 regard to the calcareous corpuscles situated in the neck of this 

 worm, I may state that narrow vessels may be easily recognized, 

 passing off" continuously from the membranous capsules infesting 

 the particles. These vascular prolongations, however, instead of 



Fig. 31. — Poi'tion of a very young Tricuspidaria nodulosa, Eudolphi ; from the intestine of a 

 pike {Esox luclus). Drawn with the aid of a camera ; X 300 diam. — Original. 



forming inosculations, — as they are represented to do by Claparede 

 in Holostomata, — are here single, having their very limited course 

 directed outwards towards the clear structureless epidermis. It is 

 highly probable that they open at the surface, but I have never 

 been able to detect the slightest indication of any aperture. 

 Dr. Guido Wagener figures a structure very analogous to this in 

 his Haarlem Prize Essay, | where the appearance occurs in the tail 

 of a larval trematode, namely, the Gercaria macrocerca of Filippi. 

 No explanation of the structure is offered in the essay itself, and it 

 becomes a very difl&cult task to interpret the phenomenon, the 

 more especially so because the tubes do not appear to have any 

 connection with the water-vascular system. 



* " Les Vers Cestoides," Plate xxii. f " Les Vers Intestinaux," Plate xxxix. 



+ " Entwickluiigs-geschichte der Eingeweidewiirmer," Plate xxix. 



