222 ON THE CLASSES OF THE 



cordingly brings us back to the Agastria, in the genus 

 Vibrio of Miiller, or those Infusoria to which belong what 

 are vulgarly known as the Eels of Vinegar. 



The most remarkable of the Intestina are the genera 

 Tarda and Botryocephalus, not only on account of their 

 being the most formidable parasites to which vertebrated 

 animals have been subjected, but also from theirprobably 

 forming a type of composite animals very distinct from the 

 compound Polypes. The classical type of the latter seems 

 to be a congeries of animals adhering to each other lateral- 

 ly ; whereas, the above compound Intestina seem to consist 

 each of a linear series of animals. It is an old but never- 

 theless to all appearance a perfectly just idea, that each 

 articulation of a Tama is a distinct animal ; for we may 

 observe each to be supplied with its peculiar organs, in 

 the shape of one or two pores and gemmiparous masses 

 placed in the middle of each lateral face of the articu- 

 lation. It is true that to the whole articulated ribband 

 which composes a Tarda there appears to be but one 

 mouth by which the nourishment common to all can be 

 received ; but we have already seen that in the compound 

 Polypes the food swallowed by one may serve to the nou- 

 rishment of the whole ; whence it may safely be concluded 

 that a Tcenia cannot be confounded with the articulated 

 Vermes, but is truly acompound animal though of a pe- 

 culiar sort. 



On the whole then we have set out from the Agastria, 

 or animals without mouth or alimentary canal, and, after 

 passing through various different types of form, are now 

 returned to the simple structure from whence we started, 

 and the Acrita have been seen to compose a circle thus 

 distributed in nature: 



