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CHAPTER XV. 



ANNUL0SA, OR WORMS. 



Under the general designation of 'Annulose' animals, or Worms, 

 may be grouped-together all that lower portion of the great Arti- 

 culated Sub-kingdom, in which the division of the body into 

 longitudinally-arranged Segments is not distinctly marked-out, and 

 in which there is an absence of those 'Articulated' or jointed 

 limbs that constitute so distinct a feature of Insects and their 

 allies. This group includes the classes of Entozoa or Intestinal 

 Worms, Rotifera or Wheel- Animalcules, Twbellaria, and An- 

 nelida; each of which furnishes many objects for Microscopic 

 examination, that are of the highest scientific interest. As our 

 business, however, is less with the professed Physiologist, than 

 with the general inquirer into the minute wonders and beauties of 

 Nature, we shall pass over these Classes (the Rotifera having been 

 already treated-of in detail, Chap, ix.), with only a notice of such 

 points as are likely to be specially deserving the attention of 

 observers of the latter order. 



484. Entozoa. — This Class consists almost entirely of Animals 

 of a very peculiar plan of organization, which are Parasitic within 

 the bodies of other animals, and which obtain their nutriment by 

 the absorption of the juices of these, — thus bearing a striking 

 analogy to the Parasitic Fungi (§§ 264-267). The most remarkable 

 feature in their structure consists in the entire absence or the 

 extremely low development of their Nutritive system, and the 

 extraordinary development of their Reproductive apparatus. Thus, 

 in the common Taenia (Tape-worm), which may be taken as the 

 type of the Cestoid group, there is neither Mouth nor Stomach, 

 the so-called 'Head' being merely an organ for attachment, whilst 

 the segments of the 'Body' contain repetitions of a complex Gene- 

 rative apparatus, the male and female sexual organs being so 

 united in each as to enable it to fertilize and bring to maturity its 

 own very numerous eggs ; and the chief connection between these 

 segments is established by two pairs of Longitudinal Canals, which, 

 though regarded by some as representing a digestive apparatus, 

 and by others as a circulating system, appear really to represent 



