100 THE STRUCTURE AND ECONOMY 



discharge its contents by the posterior orifice, in the manner 

 described by Nordman in Diplostomum Volvens* 



From the movements of the walls of this receptacle, or from 

 contractions of the animal itself, an active motion of the particles 

 of its contents is occasionally observed. The movements occa- 

 sionally resemble very much those produced by cilia. This sac 

 is apparently a secreting organ, and is probably the only arrange- 

 ment by which feculent matter is removed from the body of the 

 animal. The food of an animal, living as this does, in a cyst, is 

 already digested by the walls of its cyst. Its food, therefore, 

 yields no mechanical feculent matter, and its intestinal tube re- 

 quires no anus. The only outlet which such an animal requires, 

 Is for chemical feculent matter, which in all animals is the pro- 

 duct of secretion, and principally of the lung, gill, or kidney. 

 This sac may, therefore, be considered as a respiratory organ, or 

 kidney. 



There is another sac, very uniform in shape and size, situated at 

 the posterior part of the body. This sac is elongated, extending 

 from near the outlet of the " cisterna chyli," forward about a 

 fourth of the length of the animal. Its posterior extremity is 

 funnel-shaped, and appeal's to me, although I have failed in 

 tracing it distinctly, to open externally along with the " cisterna 

 chyli." It appears to possess circular fibres, which constrict it 

 slightly at regular distances. The three anterior fourths of its 

 wall are so thick that the cavity appears linear. This thick part 

 of the wall exhibits an arrangement of fibres or particles perpen- 

 dicular to its surface. The thick portion terminates by forming 

 a curved projection into the thin posterior part of the organ, the 

 whole arrangement resembling the projection of the human os 

 uteri into the vagina. This organ in its relations and structure 

 appears to be the analogue of the cavity described by Professor 

 Owen, as opening into the posterior orifice of Distoma clavatum, 

 and supposed by him to be a respiratory organ. 



A pyriform sac, communicating with the exterior, by the pore 

 in front of the acetabulum ; and two large, with occasionally two 

 smaller globular masses, would appear to be the analogues of the 



* Nordman. " Micrographische Beitrage" page 38, hft. 1. 



