128 



EPIZOA. 



CHAPTER X. 

 EPIZOA. 



(167.) Not only are the internal parts of living animals occasion- 

 ally made the residence of creatures adapted by their organization to 

 live under such circumstances, but there is an extensive class of 

 beings destined to an equally parasitical life, so constructed as to 

 be capable of attaching themselves to the external parts of other 

 creatures, from which they suck the nourishment suited to their 

 nature. 



These parasites are commonly found to infest Fishes, Crustaceans, 

 and other inhabitants of fresh and salt water ; generally fixing 

 themselves in positions where an abundant supply of animal juices 

 can be readily obtained, and where, at the same time, the water in 

 which they are immersed is perpetually renewed for the purpose of 

 respiration. The gills of fishes, therefore, offer an eligible situa- 

 tion for their developement, as do the branchiae of the lobster ; or 

 they are sometimes found attached in great numbers to the interior 

 of the mouth in various fishes, deriving from its vascular lining, or 

 from the abundant secretions met with in such a locality, a plentiful 

 supply of food, while they are freely exposed to the currents of 

 water which the mode of respiration in the fish brings in contact 

 with them. 



(168.) Allied, however, as these creatures are in the nature of 

 their mode of life to the entozoa, it is easy to perceive that, from 

 their residence upon the surface of the body, they enjoy a far greater 

 capability of action, and a more enlarged intercourse with the ex- 

 ternal world ; so that we are not surprised at finding them possessed 

 of organs which in both the Sterelminthoid and Ccclelminthoid 

 entozoa would have been entirely useless. In none of the indi- 

 viduals of either of those classes, therefore, have we found external 

 organs developed ; but in the Epizoa* we perceive, in a very in- 

 teresting form, the first sproutings as it were of articulated mem- 

 bers, which in higher classes attain their perfect developement. 



The least elaborately organized of these animals exhibit, indeed, 

 exceedingly grotesque and singular shapes, resembling rather im- 



* E*v, upon ; wv, an animal. 



