STERELMINTHA. 



97 



the body, where it ends in a narrow duct, which opens externally 

 at h. It would seem therefore that the last-mentioned opening 

 is the only excretory passage from the ovarium ; the connection 

 apparent in the figure, between the common sac (b) and the root 

 of the proboscis, being merely of a ligamentous character. 



(129.) The generative system of the male Echinorynchus is re- 

 presented in fig. 41, 2. The organs which secrete the fecundating 

 fluid (y, g) are two cylindrical vesicles attached at one extremity 

 by minute filaments to the walls of the body : from each of these 

 arises a duct (A), and the two, uniting at t, form a common excretory 

 canal. This canal speedily dilates into a number of sacculated 

 receptacles in which the secretion of the testes accumulates, and 

 from them a duct leads to the root of the penis (m). The penis 

 or organ of intromission, when extended, protrudes through the 

 aperture p, placed at the anal extremity of the body ; but when 

 retracted it is folded up, and lodged in a conical sheath (o). The 

 protrusion and retraction of this part of the male apparatus is 

 effected by a very simple mechanism : two muscles, (/, /,) arising 

 from the inner walls of the body, are inserted into the base of the 

 sheath, (m,) and serve to draw it inwards ; and two others, (w, w,) 

 inserted at the same point, but arising from the posterior ex- 

 tremity of the animal, by their contraction force outwards the 

 intromittent organ, an arrangement precisely corresponding with 

 that by which the movements of the proboscis are provided for. 



(130.) In Distoma perlatum 

 (fig. 42), we have another example 

 of organization intermediate be- 

 tween that which is most usual 

 among the STERELMINTHA, and 

 what we shall afterwards meet 

 with in the more perfect entozoa. 

 The animal in question resembles 

 most closely in its outward form 

 the liver-fluke of which we have 

 already spoken, and possesses a 

 similar suctorial apparatus. In 

 the annexed figure (fig. 42), the 

 oral disc only is seen, the ventral 

 sucker having been removed for 

 the sake of displaying the interior 

 of the animal, as in the diagram of 



