CHAPTER XV. 



ANNULOSA, OE WOEMS. 



356. Undbe the general designation of "annulose" animals, or 

 Worms, may be grouped together all that lower portion of the 

 Articulated 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 

 alhes. This group includes the classes of JEntozoa or Intestinal 

 "Worms, Rotifer a or Wheel- Animalcules, Turhellaria, and Anne- 

 lida; each of which furnishes many objects for Microscopic ex- 

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

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

 vnth 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. 



357. -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 (§§ 209-212). The most remarka- 

 ble 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 attach- 

 ment, whilst the segments of the "body" contain repetitions of 

 a complex generative 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 repre- 

 senting a digestive apparatus, and by others as a circulating 

 system, appear really to represent the "water-vascular system," 

 whose simplest condition has been noticed in the Wheel-animal- 

 cule (§ 278). Few among the recent results of niicroscopic in- 

 quiry have been more curious, than the elucidation of the real 



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