64 



THE VITAL FUNCTIONS, 



system, as the criterion of the individuality of that system, 

 a view which would lead us to consider the entire polypus, 

 or mass composed of numerous polypes, as a single indivi- 

 dual animal; for there is no more inconsistency in supposing 

 that an individual animal may possess any number of mouths, 

 than that it may be provided with a multitude of distinct 

 stomachs, as we shall presently find is actually exemplified 

 in many of the lower animals. 



Some of the Entozoa, or parasitic worms, exhibit a gene- 

 ral diffusion, or circulation of nourishment through numerous 

 channels of communication, into which certain absorbing 



248 



vessels convey it from a great number of external orifices, or 

 mouths, as they may be called. This is the case with the 

 Tasnia, 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 pro- 

 vided with a tube (o,) having external openings for imbibing 

 nourishment from the surrounding fluids. Although each 

 segment is thus provided with a nutritive apparatus, com- 

 plete within itself, and so far, therefore, independent of the 

 rest, the individuality of the whole animal is sufficiently de- 

 termined by its having a distinct head at one extremity, pro- 

 vided with instruments for its attachment to the surfaces it 

 inhabits. 



