NUTRITION IN THE ENTOZOA. 



83 



Some of the Entozoa, or parasitic worms, ex- 

 hibit a general difFiision, or circulation of nou- 

 rishment through numerous channels of commu- 



nication, into which certain absorbing vessels 

 convey it from a great number of external ori- 

 fices, or mouths, as they may be called. This is 

 the case with the TcBnia, or tape worm, which is 

 composed of a series of flat jointed portions, of 

 which two contiguous segments are seen, highly 

 magnified, in Fig. 247, exhibiting round the 

 margin of each portion, a circle of vessels (v), 

 which communicate with those of the adjoining 

 segments ; each circle being provided with a 

 tube (o), having external openings for imbibing 

 nourishment from the surrounding fluids. Al- 

 though each segment is thus provided with a 

 nutritive apparatus complete within itself, and 

 so far, therefore, independent of the rest, the 

 individuality of the whole animal is sufficiently 

 determined by its having a distinct head at one 



