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CHAPTER XIX 



WORMS 



I 



UNDER the general designation of Worms many naturalists still 

 group a number of Metazoa, which differ considerably among them- 

 selves, and exhibit on the one hand very simple, and on the other 

 somewhat complex plans of organisation ; the assemblage is, indeed, 

 hardly anything else than a zoological lumber-room, from which, 

 with the progress of research, group after group may be expected to 

 be removed. Among others there are included in it the Entozoa or 

 intestinal worms, the Rotifera or wheel-animalcules, Turbellaria, and 

 Annulata, 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 morphologist 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, Chapter XIII) with only a notice of such points as 

 are likely to be specially deserving the attention of observers of the 

 latter order. 



Entozoa. This term is one which has been applied to such worms 

 as 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. 1 The most re- 

 markable 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 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 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 fertilise 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 appear to represent the 

 ' water-vascular system,' whose simplest condition has been noticed 

 in the wheel-animalcule. Few among the striking results of micro- 

 scopic inquiry have been more curious than the elucidation of the 

 real nature of the bodies formerly denominated cystic Entozoa, which 



1 The most important work on human entozoic parasites is that by Professor 

 Leuckart, Die menscJiliclien Parasiten, of which a second edition is now in course 

 of publication ; of this the first portion has been translated into English by 

 Mr. W. E. Hoyle. 



