FASCIOLA HEPATICA. 157 



attaining a diameter of 3^0". I find tlie larger ones to measure 

 ftdly 3-^3". 



In addition to these corpuscles, the vessels include a more or 

 less abundant, transparent, watery fluid, in which the above- 



YiGr. 35. — Closed extremity of a water- vessel in Fasciola hepatica (x 260 diam.). — Original. 



mentioned bodies float freely. It is not improbable that the ducts 

 contain vibratile cilia, but I am not aware that they have been 

 actually demonstrated in Fasciola, although they have been seen in 

 the excretory system of other entozoa. The walls of the vessels, 

 according to my own observation, consist of a single layer of 

 transparent polygonal cells, specialised apparently from the ordinary 

 parenchyma of the body. Certainly this excretory system cannot 

 be regarded as a true circulatory apparatus, for the median trunk is 

 totally unlike the contractile dorsal vessel of leeches and other 

 annehds. A true blood-system is entirely wanting. 



Besides the foregoing structures, Leuckart mentions the 

 occurrence of another set of organs, which he calls cutaneous 

 glands. They form a thick layer of cells with granular contents, 

 varying from wo" to M' in breadth, and having a distinct, bright 

 nucleus measuring -m' in diameter. This layer is freely traversed 

 by the terminal twigs of the aquiferous system, with which 

 Leuckart thinks they may have some connection, although this 

 union could not be actually demonstrated. 



The most important, however, of all the internal organs of the 

 hermaphroditic liver fluke are those concerned in the reproductive 



