192 THE MICROSCOPE AND ITS REVELATIONS. 



CHAPTEK XVII. 

 ANNULOSA, OR WORMS. 



589. UNDER the general designation of ' Annulose ' animals, or Worms, 

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

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

 arranged segments is not distinctly marked-out, and 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, Turbellaria, and 

 Annelida; each of which furnishes many objects for Microscopic exami- 

 nation, that are of the highest scientific interest. As our business, how- 

 ever, 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. xi. ) 

 with only a notice of such points as are likely to be specially deserving 

 the attention of observers of the latter order. 



590. 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 

 ( 312-316). The most remarkable feature in their structure consists in 

 the entire absence or the extremely low development of their nutritive sys- 

 tem, and the extraordinary development of their reproductive apparatus. 

 Thus, in the common Tcenia (' 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 seg- 

 ments of the 'body' contain repetitions of a complex generative appa- 

 ratus, the male and female sexual organs being so united in each as to en- 

 able 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 represent- 

 ing a digestive apparatus, and by others as a circulating system, appear 

 really to represent the ' water- vascular system/ whose simplest condi- 

 tion has been noticed in the wheel-animalcule ( M9). Few among the 

 recent results of Microscopic inquiry have been more curious, than the 

 elucidation of the real nature of the bodies formerly denominated Cystic 

 Entozoa, which had been previously ranked as a distinct group. These 

 are not found, like the preceding, in the cavity of the alimentary canal 

 of the animals they infest; but always occur in the substance of solid 

 organs, such as the glands, muscles, etc. They present themselves to the 

 eye as bags or vesicles of various sizes, sometimes occurring singly, some- 



