H.—4.

existence of that specific parasite would come to an end. If we read through the records of destructive epidemics which have attacked man and the domestic animals we shall find that, though the number of deaths may bfe large, yet it is but small as compared with the number of individuals left alive. The disease takes its proportion of victims—it may be a very high proportion in certain localities—but if we extend our view so as to take in a wide district, we find that the tax seldom amounts to 10 per cent, of the species affected. I may mention here, as an example of a destructive epidemic, that the loss of sheep from liver-fluke in the British Isles in the winter and spring of 1879-80 was estimated at three millions, or about 10 per cent, of the total number of sheep. But that season was one of a succession of wet years, and the disease was unusually prevalent, che losses in an average year being one million, or about 3J- per cent. These losses were unequally distributed, for in some localities the disease was not known, in others.it was severely felt. One of the most prominent characteristics of parasitic diseases is their unequal development in different localities and in different seasons. So with reference to the diseases due to the bladderworm and liver-coccidia, we may expect in some localities a more extensive development and useful results, whilst in other localities the diseases may not meet with the necessary conditions, and little or no good may result. Further, we have seen that moisture is favourable to the spread of these diseases : we may expect them therefore to be more prevalent in moist or ill-drained localities, arid to be more useful in wet seasons and climates than in dry ones. Hence over a great part of Australia the diseases would be less effective than in New Zealand. When animals of the same kind..are densely crowded together on the same ground, as is the case with the rabbits in the infected districts, one of the conditions for the spread of a parasitic or infectious disease is best fulfilled. When the number of animals is reduced the danger of infection will diminish. 5. Summary. 1. The reduction of the rabbits in the Wairarapa has been chiefly due to measures adopted by man. The most valuable of these measures has been the winter poisoning, which has been followed up during the rest of the year by trapping, &c. Cats and ferrets, too, seem to have done good work. 2. Certain parasitic diseases have appeared in the district, and have been widely though unequally prevalent. 3. Of these parasitic diseases two only—those due to bladder-worm and liver-coccidia—deserve special notice as being capable of destroying rabbits. There is reason to believe that these have assisted to a small extent in destroying rabbits in the district. 4. The employment of the liver-coccidia for the destruction of rabbits cannot be advocated, as in rare instances the parasites have been known to attack man. They are, however, present in the district, and it would probably be impossible to suppress them. Fortunately, the danger to human beings is very small indeed, and the disease may prove of further use in killing rabbits. 5. The bladder-worm may be usefully employed against the rabbit-pest; but it must not be expected that it will destroy more than a small percentage of the rabbits in the district. Like all parasitic diseases, it is variable and apparently capricious in its distribution, and its propagation is limited by conditions which will vary with locality and season. It would be more useful in a moist climate than in one which is hot and dry. It assuredly cannot be regarded as furnishing alone a sufficient means of dealing with the rabbit-pest, nor will it render unnecessary the ordinary methods of the destruction of rabbits, but must be looked upon as simply a minor and auxiliary means of destruction.

DESCRIPTION OP PLATES. Plate I.—lllustkates the Bladdeb-wobm ob CcenoßUS Stage ih the Rabbit. Fig. 1, Egg of Tcenia serialis, showing the six-hooked embryo within the egg-shell. Magnified 630 diameters. Pig. 2. Embryo freed from the egg. As this is a view, from the side, one of the lateral pairs of hooks is not represented. Magnified G3O diameters. Pig. 3. Portion of muscle from rabbit showing the tracks made by the bladder-worms during the early stages of their development. At the enlarged end of each track a minute bladder-worm is to be seen. The rabbit had been fed with tape-worm eggs thirteen days previously. Natural size. Pig. 4. Young bladder-worms at early stages of their development: (a) Prom a rabbit thirteen days after it had been fed with eggs of tape-worm; (b) three weeks after infection of a rabbit; (c) four or five weeks. All natural size. Pig. 5. Young bladder-worm (about six weeks old), showing the " heads " in an early stage of development (about forty " heads " are present in rudiment). They show a radial arrangement from the first. Magnified 4J diameters. Fig. 6. Rabbit which had been infected with eggs of Tcenia serialis. It shows a large swelling on the left side of the face, the white fur towards the angle of the jaw being brought into view by the swelling. This was subsequently proved to be due to the presence of a bladder-worm. Prom a photograph taken ninety-five days after infection. Pig. 7. Two bladder-worms of small size but carrying mature tape-worm heads. The bladder-worms have been hardened in spirit and then divided by a razor longitudinally. Those halves only are shown which bear the heads. Prom rabbit which died one hundred days after infection. Natural size, from a photograph. Pig. 8. A large bladder-worm, opened and pinned out to show the " heads "on its inner wall. The " heads " here are larger than in Pig. 7, and are much more numerous (about 740). Natural size, from a photograph. Fig. 9. A group of four " heads," or " head-sacs," showing how the mouth of sac opens on the outer surface of the bladder-worm. Magnified 10 diameters. Pig. 10. A vertical section through a head-sac, showing the tape-worm head in the position in which jt is developed— i.e., inside out. At the end of the cavity of the sac (which usually has a more spiral direction than ia here shown) are to be seen the rostellum, with a portion of the crown of hooks and two of the suckers. Magnified 60 diameters. Pig. 11. Shows two head-saes— (a) with head in position in which it is developed; (b) sac turned inside out, so that the head now assumes its proper position. Drawn with camera lucida. Magnified 10 diameters. Pig. 12. A group of bladder-worms produced by budding from a single original bladder-worm. Some of them are free, others are still attached by a wide or slender stalk. About natural size. 3—H. 4.

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