The next fluke I have to notice (Distoma Campula) is better known to me. In the twenty-second volume of the ‘Linnean Society’s Transactions’ I first described this new fluke, having secured numerous examples from the peripheral branches of the biliary ducts of a porpoise (Phocæna communis). The apparently healthy cetacean was shot by Mr Jardine Murray in the Firth of Forth, in April, 1855. I mention its condition because the bile-ducts were found to be diseased in a way similar to that ordinarily observed in cases of fluke-rot affecting sheep, cattle, and other animals. In my MS. note-book I remarked: “The liver-ducts were in several places thickened and knotted near the surface of the organ. On opening these they were found to be loaded with small distomata.” It was added that, so long as the flukes were alive, they displayed under the microscope a “double and peculiar intestinal tube,” the skin being clothed with spines arranged throughout with perfect regularity. When the superficial ducts were dissected out they presented a distinctly beaded appearance, the enlargements of the lumen being occupied by flukes closely packed together. At least twenty were found in one spot. One of these enlarged ducts is figured in my recent paper to the Linnean Society (quoted below). The most striking feature connected with the structure of Distoma Campula is the twisted condition of the digestive canals. They present a zigzag appearance, the lateral folds being so sharp that they seem to constitute, as it were, a transition between the ordinary simple intestinal tubes of a true Distoma and the branched tubes seen in Fasciola. This led me originally to place the worms in a distinct genus (Campula). Perhaps there were no sufficient grounds for this generic separation; but in all Dr Anderson’s specimens obtained from the liver-ducts of the Gangetic dolphin more or less decomposition of the contents of the intestinal tubes had occurred, consequently the angular appearance of the folds is entirely lost. From the other characters presented by the worms I believe that these flukes from the Ganges are specifically identical with those originally obtained from the porpoise of the Firth of Forth. For reasons elsewhere stated at full length I have merged my genus Campula into that of Distoma. Thus, Campula oblonga is a synonym only. I cannot here treat of the morphology of trematode organisation as it deserves; but in relation to the question of transition-forms I may remark in passing that an extreme degree of intestinal folding seems as if it must result in branching. This, I think, would happen should any departure from the central distome type be rendered necessary by the exigences of the creature. At all events, the spirally-twisted and branched digestive organs constitute different ways in which nature attains one and the same end. I may add that this coiled condition of the tubes in D. Campula is by no means unique, since I have seen it in other trematode forms, as, for example, in my D. compactum from the Indian ichneumon. Dr Anderson’s specimens of D. Campula furnish a good general view of the reproductive organs. They show that the single, relatively narrow, and unbranched uterine canal is of great length, and coiled upon itself in a very tortuous manner. In this way the duct passes from side to side, crossing the central line of the body at least a dozen times, whilst every fold is likewise bent upon itself to such an extent as to increase its length to at least four times that of the animal. In short, the uterine folds may be described as passing from side to side, each separate coil being twisted upon itself so as to form secondary coils. In the fluke here drawn I have accurately represented every winding of the duct, from its vaginal outlet above to its termination, where it is joined by the ovarian and vitelligene ducts in the ordinary way. Only the merest traces of these smaller channels were visible; but the two oval testes were well defined, occupying a position somewhat lower down than usual. There was a third organ, apparently the ovary. This was less well defined, and situated higher up in the middle line. The vitelligene glands occupied the usual position. The terminal cells or capsules with their efferent ducts were well seen in several specimens. The water-vascular system was constantly visible, or at least that part of the main channel which expands into a large vesicle immediately above the central point of the tail. At this part several of the specimens ruptured. In all of the worms the lower end exhibited a sort of tail, resulting from post-mortem changes. None of the Edinburgh specimens of Campula displayed either the slightest trace of this projection or of the water-vessel connected with it. The uterine duct was filled with eggs. Approximately, the ova gave a measurement of 1/1000″ from pole to pole by 1/2100″ in breadth. Although in Anderson’s specimens the integumentary spines had fallen off, they are still attached in my original specimens from Edinburgh. The spines average 1/500″ in length. With their shafts directed downwards they separately presented the form of a long cone, the base of which was only 1/1000″ broad. After describing the above-mentioned trematodes I received a letter from Dr Anderson, in which he enclosed a sketch of a parasite taken from the small intestine of another Platanista. The illustration evidently represented a new species of cetacean fluke which I called Distoma Andersoni, with the following diagnosis:—“Body oblong, smooth externally, uniform in thickness, six times as long as broad; head with lateral projections; ventral sucker large and prominent; neck much constricted; tail evenly rounded off, blunt. Length 1/8″, breadth about 1/50″.” This worm, which was discovered by Anderson, in March, 1873, is figured in my memoir communicated to the Linnean Society. Only one parasite was found. The figure in question shows that in this species the testes are globular and placed high up in the middle line of the body. A small lobed gland immediately above the testes is probably the ovary. The vitelligene glands are largely developed. In the year 1858 Van Beneden described a large fluke from the pike-whale (Balænoptera rostrata). The specimens were from Eschricht’s collection and had been removed from the liver. As some of the examples measured no less than 80 millimètres, Van Beneden described them as “the largest known distomes.” This is probably correct, but the great human fluke (D. crassum) reaches 21/2″, and the giraffe’s fluke (Fasciola gigantea) 3 inches in length. The curator of the Australian Museum, at Sydney, Mr Gerard Krefft, mentions a Distoma which himself and Mr George Masters obtained from Delphinus Forsteri. Not improbably it represents a new species. Of the single-suckered flukes, Creplin in 1825 obtained Monostoma plicatum from the intestines and œsophagus of a northern whale. This cetacean was obtained on the coast of the island of Rugen, in the Baltic. It has been variously spoken of as Balæna borealis or B. rostrata, but by Van Beneden this cetacean is called Balænoptera musculus. The flukes exceeded 1/4″ in length. Another species of monostome (M. delphini) was vaguely indicated by Blainville as occupying the cutaneous follicles of Delphinus Dalei, which cetacean is a synonym of Micropteron sowerbiensis. The same worm is supposed by Van Beneden to infest the bottle-head (Hyperoodon butzkopf), and perhaps it was the same or a similar worm which Poelman found in the flesh of Lagenorhynchus Eschrichti. By naturalists imperfectly acquainted with helminths, the monostomes are apt to be confounded with Cysticerci; nevertheless, these widely different types may coexist in the same host. The presence of larval cestodes has been indicated in various whales. Thus, F. Cuvier and Van Beneden state that Surgeon-Major Carnot, in 1822, found an enormous quantity of small hydatids in the nasal sinuses of a porpoise (Phocæna compressicaudata). These are supposed to be Cysticerci. In like manner Mr F. D. Bennett, in 1837, obtained numerous capsuled Cysticerci from the skin and blubber of Catodon (Physeter) macrocephalus. It is unfortunate that so few of the cetacean helminths find their way into the hands of persons competent to decide upon their true character.
Fig. 69.—Diphyllobothrium stemmacephalum. a, Head, neck and upper part of the strobile; b, front, and, c, profile views of the head. Enlarged. Original.
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.