NEMATODES AND TREMATODES 945 



their existence, but leave their host for the purpose of maturing 

 their generative products ; in these later stages the Gordius is fre- 

 quently found in large knot-like masses (whence its name) in the 

 water or mud of the pools inhabited by the insects in which the 

 earlier stages were passed. The A nguillulce are little eel-like worms, 

 of which one species, A. fluviat His, is very often found in fresh water 

 amongst Desmidice, (Jonfervce, &c., also in wet moss and moist earth, 

 and sometimes also in the alimentary canals of snails, frogs, fishes, 

 insects, and larger worms ; whilst an allied species, Tylenchus tritici, 

 is met with in the ears of wheat affected with the blight termed the 

 'cockle; ' another, the A. ylutin-is (A. aceti), is found in sour paste, 

 and was often found in stale vinegar, until the more complete 

 removal of mucilage and the addition of sulphuric acid, in the 

 course of the manufacture, rendered this liquid a less favourable 

 ' habitat ' for these little creatures. A writhing mass of any of these 

 species of ' eels ' is one of the most curious spectacles which the 

 microscopist can exhibit to the unscientific observer ; and the 

 capability which they all possess (in common with Rotifers and 

 Tardigrades) of revival after desiccation, at a very remote interval, 

 enables him to command the spectacle at any time. A grain of 

 wheat within which these worms (often erroneously called Vibriones) 

 are being developed gradually assumes the appearance of a black 

 peppercorn ; and if it be divided the interior will be found almost 

 completely filled with a dense white cottony mass, occupying the 

 place of the flour, and leaving merely a small place for a little 

 glutinous matter. The cottony substance seems to the eye to consist 

 of bundles of fine fibres closely packed together ; but on taking out 

 a small portion, and putting it under the microscope with a little 

 water under a thin glass cover, it will be found after a short time (if 

 not immediately) to be a wriggling mass of life, the apparent fibres 

 being really Anyuillulce or 'eels' of the microscopist. If the seeds 

 be soaked in water for a couple of hours before they are laid open, 

 the eels will be found in a state of activity from the first ; their 

 movements, however, are by no means so energetic as those of the 

 A. ylutinis, or ' paste eel.' This last frequently makes its appearance 

 spontaneously in the midst of paste that is turning sour ; but the 

 best means of securing a supply for any occasion consists in allowing 

 a portion of any mass of paste in which they may present themselves 

 to dry up, and then, laying this by so long as it may not be wanted, 

 to introduce it into a mass of fresh paste, which if it be kept warm 

 and moist will be found after a few days to swarm with these curious 

 little creatures. 



Besides the foregoing orders of Entozoa, the Trematode group, 

 which is more closely allied to the Cestoda than to the ISTematodes, 

 must be named ; of this the Distoma kepaticum, or ' fluke,' found 

 in the livers of sheep affected with the ' rot,' is a typical example. 

 Into the details of the structure of this animal, which has the 

 general form of a sole, there is no occasion for us here to enter ; 

 it is remarkable, however, for the branching form of its diges- 

 tive cavity, which extends throughout almost the entire body, very 

 much as in the allied Planariw (fig. 714) ; and also for the curious 



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