Mr Bennett’s “find” was originally stated to have been made in Balæna mysticetus, but Van Beneden refers it to the northern sperm-whale or blunt-headed cachalot. The naturalist Bosc noticed a larval cestode found in the fatty tissues surrounding the reproductive organs of Delphinus delphis. He called it an hydatid (Hydatis), and Rudolphi placed it with the Cysticerci (C. delphini). According to Van Beneden the parasite in question is probably a sexually-immature example of the Phyllobothrium delphini described by his son. Edouard Van Beneden found this scolex in great abundance in a dolphin (Delphinus delphis), which he dissected at Concarneau in 1868. The sexually-mature state of this worm is, as the Belgian savans remark, to be looked for in some one or other of the larger sharks. The Phyllobothrium has also been found in the black fish, tursio, or high-finned cachalot (Physeter tursio). M. Gerrard Krefft has described a cestode from the stomach of a dolphin (Delphinus Forsteri), which he terms Tænia Forsteri. The strobile only measured 21/2″ in length. It is just possible that the worm may be identical with the species found by Schott. Unfortunately M. Krefft did not find any ova, and his figures do not indicate the position of the reproductive pores, if, indeed, they were present. In this place, therefore, it is fitting to remark that, under the name of Tetrabothrium triangulare, Diesing has furnished the diagnosis of a small cestode found by Schott in Delphinus rostratus off the coast of Portugal. The strobile measured only two or three inches in length, and showed a uniserial disposition of the reproductive pores. Remarking on this species Van Beneden has stated that this is the only sexually-mature tapeworm hitherto encountered in the intestines of the cetacea. This observation, made in 1870, is somewhat unfortunate, because I had already, in the year 1855, described a very large and mature form of cestode (Diphyllobothrium stemmacephalum) from the common porpoise (Delphinus phocæna). As stated by me to the Linnean Society in December, 1857, the small intestine of this porpoise was completely choked for the space of eight or nine feet by fine tapeworms so closely packed together that the gut presented the appearance of a solid cylinder. The same porpoise yielded the flukes already described (D. Campula). As afterwards remarked in my treatise on the ‘Entozoa’ (1864), four of the tapeworms measured, respectively, from 7′ to 10′ in length, the fifth example being relatively small (18″ only). For a full description of the worm I must refer either to the Linnean ‘Transactions’ or to my introductory volume whence the figures here given are taken. Five of the finest examples of this remarkable cestode have been added to the small collection of entozoa which I prepared for the Museum of the Middlesex Hospital Medical College. The head of this large cestode is excessively minute. The same cetacean host not only yielded these new cestodes and flukes, but also great numbers of the well-known strongyloid lung-worms, called Prosthecosacter inflexus and P. convolutus. Another species (P. minor or Pharurus minor) also infests the porpoise, and a fourth (P. alatus) the narwhal. As I have elsewhere observed (‘Entozoa,’ p. 91), the three first mentioned forms are readily distinguishable from each other by their relative size and length, and also more especially by the form of the tail. The females of P. inflexus attain a length of nine inches, and those of P. convolutus may be upwards of 11/2″ in length, whilst those of P. minor do not exceed an inch. The species described by Leuckart, from Monodon monoceros, is only half an inch long. All the forms infesting the porpoise were met with by Professor Quekett, and one of them has been carefully anatomised by Professor Busk. Probably several other species will be discovered when the lungs and cranial sinuses of the larger cetacea are carefully examined for this purpose. The form (P. convolutus) here represented is the least known of the three infesting the porpoise. This species has been dissected by Kuhn and Eschricht, whilst the other species have not only been examined by these authors, but also by Raspail, Dujardin, Von Siebold, Van Beneden, Leidy, and several other helminthologists. Some of Professor Busk’s examples of the male worm (P. convolutus) were fully fifteen lines long, yet, from the condition of the internal reproductive organs, he was led to believe that they were not quite fully grown. I cannot here repeat the anatomical details given in my former work, but I may add that all the species of this genus reproduce viviparously. If the worms are examined in the fresh state the young may occasionally be seen escaping by the vagina. Professor Van Beneden noticed this phenomenon in Prosthecosacter inflexus, and the same thing was observed by Busk in P. convolutus. In the instance here drawn (Fig. 71) one of the embryos is in the act of emerging, its caudal extremity being still lodged within the vulva of the parent. In the fresh worm one may also see, under the magnifying glass, numerous young worms coiled together within the oviduct; the last-named organ widening out into a capacious sac at a little distance above the end of the tail. The embryos measure about 1/300″ by 1/5000″ in breadth. Higher up, within the uterine and ovarian ducts, the ova may be seen in all stages of development, according to the particular region of the tube under examination. In their full-grown condition the eggs have a longitudinal diameter of 1/1100″ by a transverse measurement of about 1/1700″.

As regards the development and migrations of the young worms, it is highly probable that the embryos enter the bodies of various fishes before they have acquired sexual maturity. Thence they will be passively transferred to the stomachs of cetacea, whence they bore their way through the tissues to the bronchi and pulmonary vessels. Though usually found in these situations they also infest the cranial sinuses. Prosthecosacter minor is frequently lodged within the cavity of the tympanum. Professor Quekett and myself, working independently, found examples of P. inflexus occupying the chambers of the heart. Under the name of Filaria inflexicaudata, Prof. Von Siebold has described yet another pulmonary nematode from the porpoise. It occupied cysts in the lung. Like the strongyloids above mentioned, the females are viviparous, but the males are destitute of any caudal hood. In the whale (Balænoptera) killed off the isle of Rugen, and already alluded to, M. Rosenthal obtained a large number of Filariæ (F. crassicauda, Creplin). To employ Dujardin’s words the worms were situated “dans les corps caverneux du pénis d’une Balæna rostrata.” The males and females measured respectively 61/2 and 13 inches in length. Several forms of ascarides are known to infest cetaceans. The species called Ascaris simplex by Rudolphi was originally procured from the œsophagus and stomach of the dolphin of the Ganges and afterwards by Albers from the common porpoise. According to Diesing the worms obtained by Dussumier from a dolphin, taken off the Maldive Islands, must be referred to the same species, but Van Beneden maintains that Dussumier’s “find” refers to a distinct species, which he calls Ascaris Dussumierii. To this view I cannot see any objection, but I think that Van Beneden’s retention of Lebeck’s Ascaris delphini as distinct from A. simplex is untenable. Speaking of examples of this entozoon received from Calcutta, I have remarked in the ‘Zoological Society’s Proceedings’ that Dr John Anderson’s collection of parasites showed four specimens of this species. The worms had been obtained from the intestines of Platanista gangetica. Singular to say, all the examples were of the female sex, the two largest measuring about 13/8″ from head to tail. The smaller worms did not exceed one inch in length. In connection with these specimens (all of which were carefully examined by me on the 28th of September, 1875) I have only to add that they presented the peculiarly flexed state of the chylous intestine described by Dujardin. As that helminthologist had accurately surmised, the Ascaris delphini of Rudolphi must be regarded as identical with this species. It is impossible to say how many distinct species of cetacean lumbricoid worms exist. Messrs Krefft and Masters found a species of Ascaris infesting a Delphinus Forsteri taken off Sidney, New South Wales. Creplin also, in 1851, described a species (A. angulivalvis) from the intestines of Balæna rostrata. The males are less than three inches long, the females measuring 31/2″. The late C. M. Diesing received from Prof. Steenstrup a notice of some nematodes taken from a narwhal (Monodon monoceros), which appeared to the Vienna authority to be scarcely different from Creplin’s worm. Under the title Conocephalus typicus Diesing has both figured and described a remarkable nematode, two inches in length, which possesses the power of retracting its conical, or, rather, mushroom-shaped head within the body, somewhat after the manner of certain Echinorhynchi. His description is based upon museum specimens that were obtained from the stomach of a dolphin (probably Delphinus delphis) captured in the Atlantic Ocean. In addition to the above nematodes some few others remain to be mentioned. Thus, the Peritrachelius insignis of Diesing was obtained by Natterer from the stomach of Delphinus amazonicus (Spix and Martius). The largest males measured 31/2″ and the females 51/2″.

Another singular parasite, named by its discoverer, Roussel de Vauzème, Odontobius ceti, was found by him in the mucus covering the bristles (fanons) of Balæna australis. The separate worms measured about 1/5″ in length only, but they occurred in very great numbers. Lastly, Van Beneden points to certain filiform worms found by Pallas in the cavity of the ear of Beluga leucas as probably representing another distinct species of nematode, which he designates Strongylus Pallasii. I suspect, however, they will only have been fine specimens of Prosthecosacter minor. Be that as it may, it is as well to be reminded that Albers and Mehlis, and also Klein, Camper, and Rosenthal, found P. minor within the tympanic cavity of the common porpoise. When looking into the Museum stores of the Royal College of Surgeons, I found many choice examples of the genus Prosthecosacter. Some few were evidently Hunterian, but others had been separately contributed by Professors Owen and Quekett.

The acanthocephalous entozoa are well represented in whales. One of the commonest species is Echinorhynchus porrigens, of which I possess specimens given me by Prof. Goodsir, who procured them from a Balænoptera rostrata, captured in the Firth of Forth. The Hunterian Collection contains examples of this worm, recorded as having been obtained from Balæna mysticetus; and also several Echinorhynchi from the pike-whale. Professor Owen regards these last-named entozoa as distinct (E. balanocephalus, Owen). Probably Hunter’s whale-worms, which resembled E. filicollis of the eider duck, and which Van Beneden has characterised as representing a distinct species (E. mysticeti), were examples of E. porrigens. The specimens set up by me for the Museum of the Royal College of Surgeons were all of Hunterian origin. The whole subject of cetacean Echinorhynchi requires revision, and would well repay special investigation. The small, oval-shaped entozoa found by Murie in a whale which Van Beneden refers to Balænoptera musculus were probably examples of a distinct species of this genus (E. Muriei). The Vienna helminthologist has described a small species (E. turbinella) obtained by Hyrtl from Hyperoodon butzkopf. The male worms measured 1/2″ in length. Another small species (F. pellucidus) was discovered by Leuckart in the intestines of Delphinus delphis, the males measuring less than 1/4″, and the females about 1/2 an inch. Lastly, under the name of Echinorhynchus brevicollis, Van Beneden has indicated another species found by Malm in the intestines of a curious whale (Balænoptera Sibbaldii) captured alive off the coast of Sweden. The Louvain savant refers to the “take” of another example of this rare whale in the Firth of Forth about the same period. A good many whales have been captured of late years off our English and Scottish coasts, but, unfortunately, very little effort has been made to collect the numerous entozoa which they undoubtedly will have contained.

The external parasites and fellow-boarders or messmates of Cetacea are almost as numerous as helminths. In this work, however, little account can be taken of them. Every naturalist is familiar with the common Cyamus balænarum, and voyagers tell us that the whales are sometimes so densely covered by these lice that they impart to the skin a white color, and so enable the fishermen to see their victims at a great distance. The Cyami and Caprellæ are closely allied forms of læmodipodous crustaceans. Professor Lütken, of Copenhagen, has enumerated about a dozen distinct species of Cyami which are parasitic upon whales. Some of the Pycnogonidæ are said to attach themselves to whales. In their young state they are known to be parasitic upon polyps. I obtained specimens of these in 1856. The barnacles found on whales are genuine messmates; when once they have attached themselves to the skin, they remain permanently fixed. Like the Cyami or true whale-lice, these parasitic cirrhipeds are so numerous that almost every cetacean host may be said to carry its own species of louse and its own species of barnacle. The classification of these creatures is an admitted difficulty, even amongst skilled crustaceologists. The genera of cirrhipeds that are parasitic upon whales chiefly belong to the genera Coronula, Diadema, Tubicinella, and Conchoderma, but in addition to these, many lernæans of the genera Penella and Lerneonema are found on whales, and also, according to Van Beneden, at least one species of Acarus. This mite (Acaridina balænarum, Van Beneden) is found on Balæna australis. Here I must stop. The limits of this work preclude my attempting a more extended notice or enumeration of the crustacean and arachnidan parasites.

Notwithstanding the known differences existing between the phytophagous manatee-dugong group and the true whales, the parasites of this remarkable order of mammals (Sirenia) will be most conveniently noticed in this place. Not much is known respecting them. A single species of Amphistome (A. fabaceum) of the usual size has been described and figured by Diesing from the cæcum and large intestine of Natterer’s manatee (Manatus exunguis), the same mammal yielding a rather peculiar nematode, Heterocheilus tunicatus. This worm possesses a complicated set of cephalic lobes and oral papillæ, which at first induced Diesing to call the genus Lobocephalus. These structures have been fully described and figured in Diesing’s account of the anatomy of the worm in the ‘Annals of the Vienna Museum.’ The males measure 11/4″ and the females up to 11/2″ in length. From the stomach of an Indian dugong (Halicore) Rüppell and several other naturalists obtained lumbricoid worms (Ascaris halicoris, Owen), the males of which measured 21/4″ and the females from four to five inches in length. Rüppell’s specimens were from the Red Sea and Owen’s from Penang. From the now extinct Rhytina Stelleri similar worms were obtained by Steller, who called them Lumbrici caudidi. Following Brandt’s nomenclature the species has since been recognised as Ascaris rhytinæ. The worms measured half a foot in length, and occupied the stomach and duodenum. They were obtained by Steller in July, 1742, the last of the Rhytinas having been seen in 1768.

Bibliography (No. 55).—Baird, “Entozoa of Cete,” ‘Brit. Mus. Catalogue,’ Index, p. 120, 1853:—Idem, “Ascaris halicoris,” in ‘Ann. Nat. Hist.,’ 1860, p. 329; see also “Description of a rare Entozoon from the Stomach of the Dugong,” ‘Proc. Zool. Soc.,’ 1859.—Beneden, P. J. van, “Les Cétacés, leurs commensaux et leurs parasites,” ‘Bullet. de l’Acad. Royale de Belgique,’ p. 348, 1870.—Idem, ‘Animal Parasites,’ 1876.—Beneden, E. van, in ‘Comptes Rendus,’ 1868.—Bennett, D., in ‘Proc. Zool. Soc.,’ 1837, p. 30.—Brandt, “Asc. dugonis and A. rhytinæ,” in ‘Bull. P.-Math. de l’Acad. Imp. des Sci. de St Peters,’ tom. v, p. 192.—Cobbold, “Trematode Parasites from the Dolphins of the Ganges, Platanista gangetica and Orcella brevirostris,” ‘Linn. Soc. Journ.,’ Zool. Div., vol. xiii, p. 35, 1876.—Idem, “Entozoa of Delphinus phocæna,” ‘Linn. Soc. Trans.,’ vol. xvii, p. 167, 1858.—Idem, “Descript. of Asc. Andersoni,” in ‘Notes on Entozoa,’ part iv, in ‘Proc. Zool. Soc.,’ March, 1876, p. 296.—Idem, ‘Catalogue of the Specimens of Entozoa in the Museum of the Royal College of Surgeons (Preps. Nos. 39–43 and 98–101),’ 1866; see also Owen, for an account of the Hunterian specimens of Echinorhynchi.—Creplin, F. C. H., “Note on a Filaria and a Monostoma from a Whale (Balæna rostrata),” from ‘Nova Acta Acad. N. C.,’ xiv, in ‘Zool. Journ.,’ 1832–34, vol. v, p. 381; and in ‘Ersch. and Grube’s Encyclop.,’ 1846, s. 172.—Idem, “On Asc. angulivalvis,” in ‘Wiegmann’s Archiv,’ 1851, s. 158.—Diesing, “On Heterocheilus and Amphist. fabaceum,” in ‘Neue Gattungen von Binnenwürmen (u. s. w.),’ ‘Annalen des Wiener Museums,’ 1839.—Idem, “Descr. of Conocephalus,” in ‘Revision der Nematoden’ (1860), from ‘Sitzungsb. d. k. Akad. d. w. math.-naturw.,’ 1861, s. 669.—Dujardin, ‘On Odontobius,’ l. c., p. 292.—Idem, ‘Ech. porrigens,’ p. 504.—Idem, ‘Fil. crassicauda,’ p. 50.—Idem, ‘Stenurus,’ p. 266.—Idem, ‘Asc. simplex,’ p. 220.—Krefft, “Parasites of Forster’s Dolphin,” in his ‘Australian Entozoa,’ from ‘Trans. Etom. Soc. of New South Wales,’ Sydney, 1871.—Lebeck, “Asc. delphini” (quoted by Rudolphi), Synops., p. 296, from ‘Neue Schriften der Berl. Gesellsch. Naturf. Freunde,’ Bd. iii, s. 282.—Leuckart, R., “On Pharurus,” in ‘Wiegmann’s Archiv,’ 1848, s. 26.—Murie, in ‘Proc. Zool. Soc.,’ 1865, p. 213.—Owen, “Asc. halicoris,” ‘Zool. Soc. Proc.,’ 1838, and in art. “Entoz.,” ‘Todd’s Cyclop.’—Idem, “On Echinorhynchi,” in his ‘Catal. of the Contents of the Roy. Coll. Surg. Museum,’ part iv, fasc. i, p. 44; and for the “External Parasites of Whales,” ibid., p. 74, 1830.—Quekett, J., “On the Anatomy of four species of Entozoa,” abstract from ‘Proc. of Micros. Soc.,’ in ‘Ann. of Nat. Hist.,’ vol. viii, 1842; also in ‘Micros. Journ. and Struct. Rec.,’ p. 125, and in the original series of ‘Trans. of the Micros. Soc. of Lond.,’ vol. i, p. 44, 1844.—Idem, in ‘Baird’s Brit. Mus. Catal. of Entoz.,’ p. 3, 1853.—Roussel de Vauzème, “On Odontobius,” ‘Ann. des Sci. Nat.,’ 1834, p. 326, and in ‘Isis,’ 1836.—Rüppell, “Entozoa Dugonis,” in ‘Abhandl. der Senkenbergschen Museums,’ i, s. 106.—Siebold, Von, “On Filaria inflexicaudata,” in ‘Wiegmann’s Archiv,’ 1842, s. 347.

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.

Part I (Aves).

A prodigious number of entozoa are known to infest birds. So far from birds being less victimised than mammals, the contrary is the case. Every now and then avian epizoötics, due to parasites, sweep off hundreds of these attractive hosts, and in some cases even nestlings are not secure from entozoal invasion. It might be supposed that predacious birds would be more liable to invasion than the graminivorous species. Such is not the case. The eagles, hawks, vultures, and owls certainly harbor a great variety of helminths, but as much may be said of the grain-feeding game birds, and still more of the water birds. Pheasants and land-fowl, grouse and partridges, are largely infested; whilst, of water-fowl, herons and plovers, rails and snipe, ducks and geese, cormorants and divers, gulls and awks, play the rôle of host to a practically infinite variety of parasitic guests. The presence of the worm-guests does not imply any previously diseased condition of the host. Shoot any water bird, say an oyster catcher (Hæmatopus), or, still better, a grebe (Podiceps), and then carefully examine its intestinal contents. You will probably find in its interior flukes and round worms, tapeworms and Echinorhynchi. Capture and examine a frog or a salamander. The result is the same, except that the cestodes would probably be absent. As for fishes, if entozoa be a proof of cachexia, then it follows that the normal condition of all piscine hosts is a diseased state. Examine any tolerably well-grown salmon, trout, pike, perch, roach, chub, carp, or barbel, and probably any one of them will contain at least three different kinds of parasites, each of which will be present in more or less considerable numbers. From what is stated above it would be obviously futile to attempt even an enumeration of the species of avian entozoa—a remark which applies almost equally to the other groups of hosts that remain for consideration. Confining our attention to a few of the more noteworthy facts, I may observe that we have no very trustworthy data respecting the power for mischief possessed by flukes. From what we know of their destructiveness in man and certain other mammals, it would be hazardous to pronounce them harmless. Scientifically, they furnish particulars of great interest. One of the most striking facts of recent study relates to Zeller’s discovery that the little cercariæ (C. exfoliata) which are contained in a peculiar sporocyst (Leucochloridium paradoxum), infesting the tentacles of a snail (Succinea amphibia), are in reality larval forms of a fluke (Distoma macrostomum) which resides in the intestinal canal of warblers (Sylviadæ). By experiment Dr Zeller reared the Distoma in question in the intestines of whitethroats (Curruca garrula), in blackcaps (C. atricapilla), and in wagtails (Motacilla). Six days after transference the Cercariæ acquired sexual maturity. The odd thing is, that as the sporocystic Leucochloridia resemble insect larvæ, they are attacked and swallowed by the birds under delusion. It is a curious example of mimetism in favor of the fluke’s welfare. To this and other equally brilliant scientific results helminthologists were gradually led up by the earlier researches of Steenstrup and Van Beneden. As remarked in my ‘Entozoa,’ ever since Steenstrup’s discovery of the fact that Cercariæ found in the bodies of water-snails were larval flukes, a peculiar interest has attached itself to this subject. Not only were the conclusions which he elicited novel in themselves, but they formed a basis for the enunciation of that interesting “law of alternate generation” with which the famous Danish naturalist’s name will ever remain associated. In all essential particulars Steenstrup’s statements have been verified.

By way of illustrating the phases of development through which the distomes pass I cannot do better than recapitulate in an abridged form the account I have previously given of Distoma (Echinostoma) militare of the snipe and curlew. This account is based on the investigations of Van Beneden, Von Siebold, and Pagenstecher. I regret that it is out of my power to reproduce the illustrations that have already appeared on this head in my introductory treatise (see ‘Entozoa,’ figs. 5 to 9 inclusive). Our Echinostoma militare produces oval-shaped eggs, which give birth to a free ciliated embryo, and this embryo produces a sporocyst or scolex by internal budding. When the sporocyst separates itself from the embryo it presents a very simple appearance, but showing already a cæcal digestive tube. The tail end is fissured, indicating an early stage of formation of caudal appendages. In the next stage we have a well-developed head and body, the tail becoming strongly pronounced. Limb-like caudal lobes project on either side, and an oral sucker makes its appearance in front. This sucker communicates with the œsophageal bulb and passes directly into the digestive cæcum, which contains a variable number of rounded particles. At this stage, also, incompletely developed Cercariæ may be seen in the perivisceral cavity. These Cercariæ are at first shapeless organisms, but after passing through a series of gradations they ultimately assume a definite form, which, in many cases, is sufficiently distinctive to enable us to refer the Cercariæ to particular species of Distoma. The older writers regarded many of the cercarians as adult flukes. In the early state these larvæ are furnished with tails. They may be seen lodged within the cavity of the body of the sporocysts, being twisted and folded in various attitudes. The Cercariæ not only exhibit a cephalic and ventral sucker, but also a dark forked line representing the digestive system. At a still further stage other structures come into view, until the perfect Cercaria displays an oral sucker, a pharyngeal bulb, an œsophagus, two alimentary cæca, a ventral sucker, a water-vascular system consisting of two main excretory ducts, and a contractile vesicle, by means of which the ducts communicate with the external surface. The tail is conspicuous and furnished with a fringe. The alimentary organs conform to the general trematode type, but before passing into the sexually-mature condition other changes are undergone. The Cercariæ part with their tails, and subsequently they encyst themselves on or within the surface of the body of some mollusk. Their pupa condition is thus arrived at. The pupa itself differs from the cercaria in presenting a double crown of hooks surrounding the head, but the other organs correspond with those already described. According to Van Beneden the hooks make their appearance immediately after encystation. In this condition it is next transferred to the intestine of some higher animal, and in this final situation it gradually acquires all those organs the possession of which will entitle it to be called a sexually-mature or adult distome. In the immature fluke we may now discern the mouth, the buccal or cephalic sucker, the pharyngeal bulb, the œsophagus, the digestive cæca, the coronal spines, the contractile vesicle, the aquiferous system of vessels, the matrices of the yelk-forming glands, and also a central mass of cellules, from which all the other reproductive organs will in due time be developed. In the adult Echinostoma militare the upper third of the body is clothed with little spines. Taking this example as illustrative of the ordinary mode of fluke development we find that a change of hosts is necessary, and that in the intermediate state they occupy the bodies of mollusks. Thus, for the continuation of the species, there must needs be a contemporaneity of vertebrate and evertebrate hosts. Surely no reasonable person can ascribe this concurrence to merely fortuitous circumstances. In this connection I may remark that Villot, in his account of the migrations of the trematodes, states that the cercarian forms of Distoma leptosomum and D. brachysomum of Tringa alpina occur in Scrobicularia and Anthura. These parasites are also found encysted in the gizzard of Tringa.

The tapeworms of birds are undoubtedly injurious to their bearers. All the worms appear to be armed with cephalic hooks; at least, such is the case with the species described by Krabbe, who has supplied figures of the hooks drawn to a scale. Dr Krabbe’s beautiful monograph is a perfect model of its kind. In the accompanying figure the hooks have fallen (Fig. 72). On account of the frequency of their occurrence, some persons have supposed that tapeworms are not injurious to their hosts, forgetting that it is not the mere fact of the existence of tapeworms, but their excessive numbers during particular seasons that give rise to avian epizoötics. The same rule holds good with other parasites. Of course, in fledgelings, as also obtains in yearlings amongst our domesticated animals, a very few parasites are sufficient to prove destructive to the bearer. Thus, as regards the so-called “grouse-disease,” during one season it may be due to tapeworms, during another to strongyles, during a third to excessive abundance of both these parasites. Unfortunately, other avian epizoötics, not necessarily due to parasites of any kind, may be mistaken for helminthic epizoöty. The same thing happens amongst quadrupeds. We have, for example, parasitic equine epizoötic outbreaks, and likewise non-helminthic equine epidemics (as in the case of the Egyptian horse plague of 1876). The true nature of any epizoöty can only be determined by competent investigation. That was well shown in the grouse epidemic of 1872. In that epizoöty the greater number of the birds succumbed to the injuries produced by a nematode worm (Strongylus pergracilis, Fig. 73), but, without doubt, the occasional presence of numerous tapeworms (Tænia calva) hastened the consequent fatality. The following table, giving the results of examination of twelve diseased grouse from the Earl of Cawdor’s estate, will show how inconspicuous a part tapeworms played in the epidemic of 1872. For further details I must refer to my brochure on the ‘Grouse Disease,’ and to some other memoirs quoted in the bibliography below.

I have said that tapeworms prove fatal to young birds, even to nestlings. A notable instance of this is recorded by Mr Eames. The parasites were examples of Tænia angulata. Apart from the epidemiological aspects of the subject, it is not uninstructive to notice the variety of helminths that infest the common fowl and game birds. Accordingly, I append a similar but more extended list than that previously given in the supplement to my introductory treatise:

In regard to this list I can only afford space to remark that several of the species are possibly mere varieties. Some of the worms are of great interest. It occasionally happens that Distoma ovatum is found in the albumen of the fowl’s egg, and it is even more common to obtain Ascaris inflexa from the same situation. For a recent example I am indebted to Dr Walker, of Peterborough. Spiroptera helicina resides in the feet, occasioning enlargement of the joints and consequent distress to the bearer. Probably the most important in the list is my Strongylus pergracilis. Here I may mention that on the 10th of April, 1878, I received a letter from Dr Manson, of Amoy, announcing his acquaintance with a filaria infesting the eye of the fowl. On the 9th of May I also received from Dr Manson the head of a bird showing examples of the worm. As the species is new to science I have proposed to call it Filaria Mansoni, after the discoverer. The male is 5/8″ and the female 3/4″ in length. Of the injurious nematodes, giving rise to avian epizoöty, probably one of the most destructive is Ascaris maculosa infesting pigeons. On the 9th of October, 1873, I received a letter from Dr J. Alexander Macdonald, of Woburn, Bedfordshire, stating that he had forwarded to me a pigeon which had been found dead on the previous morning. It seems that the owner of the bird had erected a large pigeon-house, and had imported a number of Antwerp smerles, these birds all continuing in a perfect state of health until about a week before the above-mentioned date, when, to use Dr Macdonald’s words “first one and then another was attacked, and so on, until four or five of the pigeons had died after a few hours’ illness.” The suddenness of these attacks not unnaturally suggested poisoning; and, accordingly, says my informant, the owner “had the curiosity to open one of the birds, when, to his astonishment, he found the intestines stuffed with worms.” Two days later I received a letter from Dr Macdonald, stating that several others of the flock had died, and it further appeared to him probable that the daily list of sick and dying would continue to increase. On the 14th of the month three more of the birds were dead. On the 4th of the following November, the same correspondent obligingly informed me that the epidemic had been “at last mastered.” It seems that altogether twelve birds had perished. On the 9th of October one of the birds was carefully examined by me, and the results were so interesting that I am constrained to give a few of the particulars originally communicated to the Zoological Society. As stated in my paper, the whole intestinal tract of the dead bird was crowded with these ascarides. The small intestine was inflamed throughout, and showed several large ulcerated patches; nevertheless, there were no traces of emaciation. From this it was evident that the parasites had grown quickly, the malady having a correspondingly rapid formation. The distribution of the parasites was curious. One specimen, two inches long, reached from the crop to the proventriculus. The cavities of this organ and of the gizzard were crammed with worms completely blocking the passage. Three of the worms had also placed themselves within the pyloric opening, their bodies partly lodging within the duodenum. The duodenum itself was crowded with worms, their numbers somewhat decreasing downwards. I removed thirty-six worms from the œsophagus, proventriculus, and stomach, besides 166 others from the intestinal canal, thus obtaining a total of no less than 202 nematodes from this small host. Considering the large size of these entozoa, the extent of infection must be pronounced remarkable. The largest females measured 21/2″ in length. One of the most interesting facts—serving to exemplify a well-known habit of lumbricoid worms generally—consisted in the circumstance that two of the parasites had succeeded in perforating the horny lining membrane of the gizzard. The injuries had been accomplished during the life of the host, for the walls of the gizzard were inflamed opposite the perforations. There was a little half digested food within the stomach, the débris of which, when placed under the microscope, showed several ova. There were no free embryos, neither had the development of the freed eggs proceeded beyond yelk-segmentation. Free eggs were also found both in the small and large intestine. The eggs measured about 1/360″ by 1/700″ in diameter. Referring to my paper for further anatomical details, I can only add that, despite these facts, the ascarides in question do not appear to be a very frequent source of epizoöty. It was remarked by Dujardin that Heister, at Rostok, and Gebauer, at Breslau, found this parasite abundant at the beginning of the eighteenth century; but, according to examinations conducted at Vienna, the worm was found in the common pigeon in only eleven instances out of 245, and thrice only in thirty-eight examples of the ring-dove; moreover, the examination of eighty-seven other pigeons and doves of different species yielded entirely negative results. The Dublin helminthologist, Bellingham, noticed the occurrence of this parasite in Ireland.