PART XII (MARSUPIALIA).

The well-known fact that, in respect of their habits, the pouched mammals epitomise, as it were, the non-marsupial quadrupeds, would naturally lead us to look for a repetition of corresponding type-forms of entozoa as guests within their bodies. Speaking generally, the inference is correct; but very few of the entozoa hitherto found in marsupials correspond, as species, with those infesting man and non-pouched mammalia. A noteworthy exception occurs in the case of the common liver-fluke, which is abundant in the great kangaroo (_Macropus major_). This fact was well known to Bremser and all the older helminthologists, and it has since been confirmed by numerous observers resident in Australia. The late Dr Rowe, an acute observer and successful stock-breeder, who wrote chiefly in connection with the sanitary bearings of parasitism, remarked that “the native animals of Australia are much infested with internal parasites. Some of those now found in the kangaroo and the smaller marsupials may have been derived from our domestic animals; but tapeworms and other internal parasites have been met with in animals occupying regions wholly unsettled.” Precisely so. That is just what we should expect. The Australian indigenous mammals have their own entozoa as a matter of course, and, in addition, they have contracted a few species from the domestic animals introduced into the country. On the whole, however, it cannot be said that the parasites of marsupials are of much practical consequence to agriculturists, since, with the exception of flukes, and probably hydatids, the Australian marsupials do not appear to harbor any entozoa that are likely to prove injurious to man and his domestic companions. The amount of fluke-germ distribution by kangaroos must be infinitesimal as compared with that proceeding from sheep and other kinds of “stock;” therefore on the score of parasitism alone it is not desirable to hasten the slaughter of kangaroos. From the scientific standpoint, it is to be regretted that the naturalists of New South Wales and other colonies have done so little towards defining the various species of marsupial entozoa. Mr Krefft, in his interesting brochure on Australian entozoa, describes a few tapeworms, and also points to several round worms which may be new to science, but with the exception of the common fluke no trematode appears to have been encountered by himself or Mr Masters in the various marsupials which they examined in the neighbourhood of Sydney and Queensland. Dr Bancroft, of Brisbane, has placed in my hands a small collection of entozoa, several of which have been obtained from marsupials, but their identification remains partly in abeyance.

Besides the liver-fluke, the only marsupial trematodes at present fairly described appear to be _Hemistoma alatum_, and two species of _Rhopalophorus_ (_R. coronatus_ and _R. horridus_). All of these were obtained by Natterer from the opossums of tropical America. One of these flukes was described at some length by Rudolphi, who called the species _Distoma coronatum_, and gave its length as varying from two to four lines. Diesing, in one of his best illustrated monographs, has shown that the opossums in question are infested by two distinct species of fluke, which must be generically separated from the distomes. These singular _Rhopalophori_ are furnished with a pair of armed retractile proboscides (Bohrüsseln), which must form powerful organs of anchorage. The worms are found attached to the walls of the stomach and small intestines.

The tapeworms of marsupials are more numerous than flukes. Thus, we have Rudolphi’s _Tænia festiva_, eight to ten inches in length, occupying the gall-bladder and hepatic duct of _Macropus giganteus_. Dr Bancroft’s collection contains two almost perfect examples of a tapeworm which he procured from a small streaked kangaroo (_Halmaturus Derbyanus_). These I have identified as _T. festiva_. In this worm the reproductive papillæ, not hitherto observed, are biserially arranged. Fragments of a tapeworm (_T. didelphidis_) are preserved in the Vienna Museum, taken from the intestines of the American _Didelphis murina_. From different species of wallaby (_Halmaturus_) Mr Gerard Krefft has given more or less complete descriptions of two tapeworms (_Tænia fimbriata_, and _T. Mastersii_), and a probable Bothriocephalus (_B. marginatus_). I am not in a position to pronounce upon the distinctness of these Australian _Tæniæ_; but I may observe that Krefft’s _T. fimbriata_ comes very near to another species which Dr Bancroft has given me. The Brisbane _savant_ obtained the worm from a koala (_Phascolarctos cinereus_). Provisionally I call this species _Tænia geophiloides_, in allusion to its general resemblance to a long millipede. The single, perfect strobile, with the head attached, measures thirteen inches in length. Prof. Leidy has furnished a description of another tapeworm (_T. bipapillosa_) from a wombat (_Phascolomys_), and Mr Krefft has described yet another species obtained from the common vulpine opossum (_Phalangista vulpina_). The single example in Krefft’s possession measures four inches in length. He has named it _Tænia phalangistæ_. Some of the American opossums (_Didelphys brachyura_, and _D. quica_) have been found to harbor a species of ligula (_L. reptans_, Diesing) in the sexually-immature state. Lastly, I find in Bancroft’s collection several tapeworms obtained from that small and interesting monotreme marsupial commonly known as the Australian hedgehog, echidna, or porcupine ant-eater of the colonists (_Tachyglossus setosus_). The strobiles, which are nearly perfect, average three inches in length, and are made of very narrow and closely-set proglottides. This species is evidently new to science, and as such I propose to call it _Tænia phoptica_, in allusion to its thick-set appearance and its consequent burdensome character to the bearer. The largest proglottides measure fully 3/8″ in width. There can be little doubt that the presence of any considerable number of such comparatively large tapeworms must seriously incommode, if they do not actually prove fatal to their unfortunate hosts.

So far as regards mere variety of species, the nematode fauna of marsupials is probably far in excess of that of the trematodes and cestodes. I cannot therefore do much more than enumerate the species. The Hunterian Museum of the Royal College of Surgeons contains the original “worms found alive within the capsular ligaments of the knee-joint of a kangaroo,” which have been indicated as _Filariæ macropodis gigantei_. It would, in my opinion, be far better to call the worm, after its discoverer, Webster’s filaria (_F. Websteri_). Dr Bancroft has likewise encountered this same parasite in the great kangaroo. From the abdominal cavity of a wallaby Leidy has also obtained a filaria (_F. spelæa_). The American opossums (_Didelphys_) are much infested by _Ascaris tentaculata_, which is found in the cæcum, and many of them also harbor a small whipworm (_Trichocephalus minutus_). Another tolerably abundant nematode (_Physaloptera turgida_) was obtained by Natterer from the stomach of _Didelphys azaræ_, _D. myosurus_, and _D. cancrivora_. The only other nematode mentioned in Diesing’s ‘Systema’ is _Aspidocephalus scoleciformis_. This is found in _D. murina_, and _D. domestica_. From the opossum of the United States (_D. virginiana_) Prof. Leidy has also obtained _Asc. tentaculata_, _Trichocephalus minutus_, and _Physaloptera_ (Spiroptera) _turgida_. According to Molin there are grounds for separating some of these stomach-worms into distinct species. Thus, he has recognised the examples found by Natterer in _Didelphys myosurus_ as belonging to the genus _Histiocephalus_, as emended by himself. If the separation be allowed, then we must add to the list Molin’s _Histiocephalus subulatus_. From Bancroft’s collection I am certainly in possession of two distinct kinds of nematode taken from the stomach of _Halmaturus Derbyensis_. I have also two species of nematode from _Macropus giganteus_. Their identification, however, is a matter for future consideration. Lastly, as regards the acanthocephalous parasites, only one species appears to have been described. This worm (_Echinorhynchus microcephalus_) was obtained by Olfers in Brazil, from the intestines of _Didelphus philander_. It also occurs in _D. virginiana_. Being a tolerably large species, that is to say 3″ in length, it seems surprising that it has not been found in the American opossums generally.

BIBLIOGRAPHY (No. 56).--_Cobbold_ (see Rowe). _Diesing_, ‘Syst.,’ l. c., p. 519; also monogr. ‘Binnenwürmen’ (l. c., Bibl. No. 55).--_Krefft, G._, ‘Australian Entozoa’ (l. c., Bibl. No. 55).--_Leidy_, ‘Proc. Philad. Acad.,’ 1856.--_Idem_, “Tapeworm from the Wombat,” _ibid._, 1875, p. 6.--_Molin_, “Una monogr. del genere Physaloptera,” p. 10, “Una monogr. del gen. Dispharagus,” and “Una monogr. del gen. Histiocephalus,” p. 37, aus dem xxxix Bd., d. ‘Sitz. d. m.-nat. Cl. d. k. Akad. der Wissensch.,’ s. 479-507 und s. 637-672, 1860.--_Rowe, J._, “Parasitism in Australia” (in which the author sought to benefit stock-owners by utilising, prophylactically, my published opinions), repr. from the ‘Melbourne Leader’ in the ‘Veterinarian,’ May, 1874.--_Rudolphi_ (in ref. to _Dist. coronatum_), ‘Synops.,’ p. 116 and 686.--_Webster_ (respecting his “Filaria,” see), ‘Catalogue of the Hunterian Collection of Entozoa,’ p. 7, prep. 49, 1866; also the old ‘Catal. of the Museum Roy. Coll. Surg.’ (by Owen), part iv, fasc. i, p. 37, No. 170; also Diesing’s ‘System,’ p. 280, and Froriep’s ‘Notizen,’ Bd. xlii, s. 328.

SECTION II.

To give an air of completeness to this treatise, I shall devote the few pages remaining at my disposal to a brief summary of the general facts of parasitism as witnessed in birds, reptiles, fishes, and evertebrated animals. For details I must refer to the separate original works and memoirs quoted in the appended bibliographies.