194: THE MICROSCOPE AND ITS REVELATIONS. 



writhing mass of any of these species of f 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, 452), of revival after desiccation, at however remote an 

 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 pepper- 

 corn; and if it be divided in two, the interior will be found almost 

 complete 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 Microscpe 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 Anguillulw, or ' eels ' of the Micro- 

 scopist. 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. glutinis 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. 



592. Besides the foregoing Orders of Entozoa, the Trematode group 

 must be named; of which the Distoma hepaticum or 'fluke,' found in 

 the livers of Sheep affected with the 'rot,' is atypical 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, how- 

 ever, for the branching form of its digestive cavity, which extends 

 throughout almost the entire body, very much as in Planariae (Fig. 406) ; 

 and also for the curious phenomena of its development, several distinct 

 forms being passed through between one sexual generation and another. 

 These have been especially studied in the Distoma, which infests the 

 Lymnc&us; the ova of which are not developed into the likeness of their 

 parents, but into minute worm-like bodies, which seem to be little else 

 than masses of cells inclosed in a contractile integument, no formed 

 organs being found in them ; these cells, in their turn, are developed into 

 independent zooids, which escape from their containing cyst in the con- 

 dition of free ciliated Animalcules; in this condition they remain for 

 some time, and then imbed themselves in the mucus that covers the tail 

 of the Mollusk, in which they undergo a gradual development into true 

 Distomata; and having thus acquired their perfect form, they penetrate 

 the soft integument, and take-up their habitation in the interior of 

 the body. Thus a considerable number of Distomata may be produced 

 from a single ovum, by a process of cell -multiplication in an early stage of 

 its development. In some instances the free ciliated larva possesses dis- 

 tinct eyes; although these organ are wanting in the fully developed Dis- 

 toma, the peculiar f habitat ' of which would render them useless. 



593. TURBELLARIA. This group of animals, which is distinguished 

 by the presence of cilia over the entire surface of the body, seems inter- 

 mediate in some respects between the ' trematode ' Entozoa and the Leech- 

 tribe among Annelida. It deserves special notice here, chiefly on account 



