From the large number of species of Echinorhynchi infesting our fresh-water fishes, they present quite a feature of piscine parasitism. Almost every perch, chub, carp, pike, barbel, bream, or roach that one opens is found to have its intestines occupied by parasites which exhibit a light yellow color. These are Echinorhynchi, the common forms being E. proteus, E. angustatus (Fig. [84], No. 1), E. clavæceps, E. globulosus, and E. tuberosus. In the Salmonidæ, besides several of the above, we may also find E. clavula, E. fusiformis, and E. pachysomus. As a group these parasites are more attractive looking than most other helminths, and they will well repay the zoological collector. The species infesting marine fishes are almost as numerous as those found in fresh-water hosts.
Bibliography (No. 59).—(Anonymous), “Note by ‘An Inquirer’ respecting Worms in Fish,” in the ‘Lancet,’ March 7, 1868, p. 336.—Baer, K. E. von, “On the Tapeworms found in the Waters of the Pregel by Linneus,” from the German, in ‘Edin. New. Phil. Journ.,’ 1829, p. 374, and in the ‘Edin. Nat. and Geo. Sci. Journ.,’ 1829–30, p. 311; also from the ‘Trans. of Nat. Soc. of Dantzig,’ in the ‘Lancet,’ 1829.—Badcock; see Slack.—Baird, ‘British Entomostraca,’ London, 1850.—Beneden, J. P. van, “Les vers cestoides,” ‘Mém. de l’Acad. Roy. de Belg.,’ tom. xxv, 1850.—Idem, ‘Mém. sur les vers intest.,’ Paris, 1858.—Idem, “On Echinobothrium,” in ‘Bull. de l’Acad. de Brux.,’ 1849.—Idem, (with Hesse), ‘Rech. sur les Bdellodes ou Hirudinées et les Trématodes marins,’ 1863–65.—Idem, ‘Rech. sur les Turbellaries,’ 1861.—Idem, “On a new Lerneonema,” ‘Bull.,’ l. c., 1851, and in ‘L’Institut,’ 1851.—Bertolus, ‘Mém. sur le développement du Dibothrium latum (Bothriocéphale de l’homme),’ App. to Dr Duchamp’s work quoted below.—Bosc, ‘Hist. Nat. des Vers,’ 1802, p. 271.—Bradley, C. L., “On the occurrence of Gyrodactylus on Sticklebacks,” ‘Proc. Linn. Soc.,’ 1861.—Brullé, “Note on the Reproduction of Ligula,” from ‘Comptes Rendus,’ in ‘Ann. Nat. Hist.,’ 1855.—Chatin, ‘On Amphibdella torpedinis from the Gills’ (l. c., Bibl. No. 57).—Chavannes, “On Fluke-larvæ from Coregonus,” in ‘Bull. de la Soc. Vaud. des Sci. nat.,’ tom. iii.—Claparède, E., “Ueber die Gattung Tetracotyle,” &c., in ‘Zeitsch. f. wiss. Zool.,’ 1857, s. 99 et seq.—Cobbold, “The Sunfish (Orthagoriscus) as a Host,” ‘Intell. Observer,’ Sept., 1862.—Idem, “Notes on the Calcareous Corpuscles of Tricuspidaria,” ‘Quart. Journ. Micr. Sci.,’ 1859.—Idem, “Notes on Tricuspidaria and Pentastoma,” ibid., 1859.—Idem, “Note on Gyrodactylus elegans,” ibid., 1862; see also Wedl.—Idem, “On Distoma clavatum from the Sword-fish,” ‘Proc. Linn. Soc.,’ 1867 (Zool. Sect., p. 200).—Idem, “Tapeworms in Trout,” letter to the ‘Field,’ July 26, 1873; see also F. Francis (below).—Idem, “Remarks on the Entozoa and Ectozoa of Fish,” the ‘Veterinarian,’ Oct., 1867, p. 671.—Idem, “On Agamonema crenilabri,” in ‘Science Gossip,’ 1876; see W. W. Wilson.—Idem, in ‘Linn. Trans.,’ 1858.—Idem, ‘Note on Parasites from the Wolf-fish (Annarhicas) and Lump-sucker (Cyclopterus), collected by Mr Devis’ (l. c., Bibl. No. 57).—Idem, “Descr. of the Scolex of a Tetrarhynchus,” in a paper on ‘Parasite Larvæ,’ ‘Intell. Observer,’ 1863.—Idem, “Synopsis of the Distomidæ,” ‘Proc. Linn. Soc.’ (Zool. Div.), 1860.—Idem, “Remarks on Bothriocephalus latus, in relation to Dr Fock’s supposition that the Bleak (Leuciscus alburnus) is concerned in its Production,” the ‘Veterinarian,’ July, 1878.—Cornalia, E., ‘Sopra una nuova specie di Crostacei Siphonostomi (Gyropeltis doradis),’ Milano, 1859.—Coughtrey, M., “On the absence of Tapeworm in the Salmon-trout of New Zealand,” letter to the ‘Otago Daily Times,’ dated from the Otago University, Dec. 6, 1875.—Diesing, ‘Vierzehn Arten von Bdellideen,’ Wien, 1858; see also ‘Revisions,’ quoted in Bibl. No. 58.—Donnadieu, A., “Étude sur les Ligules,” in ‘Archives Zool. Expériment.,’ 1876.—Duchamp, G., ‘Recherches anat. et physiol. sur les Ligules,’ Paris, 1876; see also Bertolus.—Fock, ‘The Bleak as a source of the Broad Tapeworm.’ See Cobbold.—Francis, F., “Tapeworm in Fish” (with report by myself), in the ‘Field,’ June 28, 1873.—Idem, in the ‘Field’ for July 12, 1873.—Garsin, ‘Histoire de l’Acad. des Sci.,’ Paris, 1730, p. 44.—Goodsir, J., “On Gymnorhynchus horridus, a new Cestoid Entozoon,” ‘Edin. New Phil. Journ.,’ p. 9, 1841.—Houghton, W., “On the occurrence of Gyrodactylus elegans in Shropshire,” ‘Ann. Nat. Hist.,’ 1862.—Huxley, “Note on Gyrodactylus,” ‘Proc. Roy. Inst.,’ April 20, 1852, and ‘Edin. New Phil. Journ.,’ 1852, p. 172.—Knoch, J., ‘Entwickelungsgeschichte d. Both. proboscideus,’ 1862.—Knox, J. F., “Note respecting the occurrence of a peculiar Microscopic Entozoon in the Textures of the Herring,” ‘Lancet,’ 1838.— Kölliker, “Zwei neue Distomen,” ‘Ber. v. d. K. Zoot. Anstalt zu Würzburg,’ 1849.—Idem, ‘Ueber Tristoma,’ ibid., 1849.—Leidy, J., “Notice of a Tetrarhynchus (T. tenuicaudatus) in the Remova;” ‘Proc. Acad. N. S. Philad.,’ Oct. 15, 1878; and in ‘Ann. Nat. Hist.,’ Feb., 1879.—Leydig, “Ueber Argulus,” ‘Sieb. und Köll. Zeitsch.,’ 1850.—Maddox, R. L., “Some Remarks on the Parasites found in the Nerves (and other parts) of the Common Haddock (Morrhua æglefinus),” ‘Trans. of the Roy. Micr. Soc.,’ 1867, p. 87.—Menzies, ‘Linn. Trans.,’ 1790, p. 187.—Miescher, “On Filaria piscium,” &c., in ‘Excerpta Zoologica,’ communicated by Dr Frances, in ‘Ann. Nat. Hist.,’ 1842.—M’Intosh, W. C., “Notes on the Food and Parasites of the Salmo salar of the Tay,” ‘Proc. Linn. Soc.,’ 1863; repr. in the ‘Zoologist,’ Feb., 1864.—Müller, J., “Note on a Parasitic Formation (Gregarina) in the Pike, with a statement from his ‘Neurologie der Myxinoiden,’ that Diplostomum rachineum is to be found alive under the cerebral membranes of Petromyzon fluviatilis,” from ‘Müller’s Archiv,’ in ‘Micr. Journ. and Struct. Record,’ p. 20, 1842.—Nardo, in ‘Heisinger’s Zeitsch.,’ 1827, s. 68, and in ‘Isis,’ 1833, s. 523.—Olsson, P., “Researches on the Flukes and Tapeworms chiefly of Marine Fishes,” ‘Entozoa, iakttagna hos Skandanaviska Hafsfiskar,’ Lund (aftr. ur ‘Lunds Univ. Årsskrift,’ tom. iii, iv), 1867–68.—Owen, ‘Zool. Soc. Trans.,’ 1835, p. 382.—Pallas, ‘Spicilegia Zoologica,’ fasc. x, p. 18, 1774.—Siebold, C. von, ‘Band und Blasenwürmer,’ s. 41, Huxley’s edit., p. 32.—Idem, “On Diplozoon paradoxum,” from ‘Zeitsch. f. wiss. Zool.’ (by Huxley), in ‘Ann. Nat. Hist.,’ 1851.—Idem, “Ueber den Generationswechsel der Cestoden nebst einer Revision der Gattung Tetrarhynchus,” ‘Zeitschr. f. wiss. Zool.,’ 1850, s. 198.—Idem, “Gyrodactylus, ein ammenartiges Wesen,” ibid., 1849.—Slack, H. J., “On Bucephalus polymorphus,” in ‘Monthly Microsc. Journ.,’ April, 1875, p. 141.—Van Beneden (see Beneden).—Verrill, A. E., “On the Parasitic Habits of the Crustacea,” from ‘American Naturalist,’ in ‘Scientific Opinion,’ Aug. 4, 1869, p. 185.—Idem, “New Flukes (Tristoma læve and T. cornutum) from the Mouth and Gills of Tetrapturus albidus,” ‘American Journ. of Science,’ p. 40, 1875.—Von Baer (see Baer).—Von Siebold (see Siebold).—Wagener, R. G., “Helminth. Bemerkungen,” in ‘Sieb. und Köll. Zeitsch.,’ 1857.—Idem, “Enthelminthica,” ‘Müller’s Arch.,’ 1851.—Idem, “Ueber Eingeweidewurm (Amphiptyches) in Chimæra monstrosa,” ‘Müll. Arch.,’ 1852.—Idem, ‘Beiträge zur Entw.-Gesch. der Eingeweidewürmer (Preisschrift),’ 1857.—Wedl, “On Gyrodactylus” (see reference to my paper on ‘G. elegans’), ‘Quart. Journ. Micr. Sci.,’ 1862; trans. from his ‘Anhang,’ “Ueber die Gattung Gyrod.,” to ‘Anat. Beobachtungen ueber Trematoden,’ Wien, 1858.—Idem, ‘Hæmatozoa in Fishes,’ &c. (l. c., Bibl. No. 58).—Wigham, R., “Note on Holostomum cuticola from Roach and Bream,” ‘Ann. Nat. Hist.,’ p. 235, 1851.—Wilson, W. W., “On a Parasitic Worm infesting a Marine Fish (Crenilabrus rupestris),” in ‘Science Gossip,’ Jan., 1876.—Yarrell, W., “Note on Tristoma coccineum,” in his work on ‘Brit. Fishes,’ vol. ii, p. 353, 1836.
Part IV (Evertebrata).
Fig. 85.—Sphærularia bombi. Showing the supposed male in sitû. After Lubbock.
Since a large proportion of all those helminths that require a change of hosts must needs pass into the bodies of insects, crustaceans, mollusks, or other evertebrated animals, it is evident that these lower creatures are almost as liable to be infested by parasites as the vertebrates themselves. As a rule, no doubt, the parasitic forms infesting individual evertebrated hosts are not numerous; nevertheless the water-snails form a noteworthy exception. Thus, some ten different species of parasite are found either in or upon the common Planorbis corneus; whilst Lymnæus stagnalis, Paludina vivipara, and P. impura, each support at least a dozen species. Of course, the parasites are not sexually mature, since nearly all of them are Cercariæ or larval trematodes. Snails, oysters, mussels, whelks, and other mollusks afford harbour and anchorage to a variety of parasites and messmates; but, fortunately, few or it may be none of the strictly human parasites require to pass through these intermediate bearers. Distoma crassum is possibly an exception. Save the cuttle-fishes, not many evertebrated animals are infested by sexually-mature worms. One of the most notable exceptions is that of a nematoid infesting bees. This worm was known to John Hunter, who spoke of it as “the animal that breeds in the humble bee.” In the year 1836, M. Léon Dufour first applied the term Sphærularia to this remarkable worm, which he discovered in the abdominal cavities of two species of bee (Bombus terrestris and B. hortorum). The worm was subsequently found by Von Siebold in two other species of bee (B. muscorum and B. sylvarum), but it remained for Sir John Lubbock to demonstrate that this parasite not only infests these insects, but also Bombus lucorum, B. lapidarius, B. pratorum, B. subterraneus, and Apathus vestalis. I possess specimens from Vespa vulgaris and V. rufa. Sir J. Lubbock and Mr. Cole have separately given full anatomical descriptions of the worm. According to Lubbock the so-called female is about an inch in length, of a whitish color, and 1/15″ in thickness, being bluntly pointed at either extremity. Sphærularia is everywhere covered by small warts or button-like projections, in all numbering about 800. The warts are transparent, each, according to Lubbock, projecting from 4/1000″ to 6/1000″ above the general surface of the integument. There is neither mouth, œsophagus, intestine, nor anus; but in their place a large fatty mass or corpus adiposum. Sir J. Lubbock remarks that this peculiar organ “is homologous, not with the whole intestinal canal of nematodes, but only with the intestine; and we find, in fact, that in Gordius the œsophagus is very short, and opens at once into the anterior end of the corpus adiposum; so that to pass from this genus to Sphærularia it would be necessary to shorten the œsophagus a little more, and then the wall of the corpus adiposum would be immediately attached to that of the body. So far, therefore, as concerns the corpus adiposum and the œsophagus, Sphærularia agrees neither with Gordius nor Mermis, nor, indeed, with one more than the other; since, if it agrees with Mermis albicans in the double series of large fat cells, it has no œsophagus, and in this respect more nearly resembles Gordius.” The reproductive organs consist of a single ovary, uterus, and terminally situated vulva. These organs in the full-grown females contain ova in all stages of development up to the condition of advanced yolk segmentation; but it does not appear that embryonic formation takes place whilst the eggs are still in utero. “The young animals are born soon after the eggs are laid. They are about 1/60″ in length, and 1/2500″ in diameter at the broadest part. Before Sir J. Lubbock conducted his inquiries the so-called male appears to have been overlooked. The male, if male it be, is extremely minute; that is to say, about 28,000 times smaller than the female.” Notwithstanding this very circumstantial account based on Lubbock’s determinations, Schneider has sought to show that the facts have been entirely misinterpreted. What Lubbock regards as the male worm is, in Schneider’s opinion, a female, whilst the so-called female is nothing more than a gigantic prolapsed uterus which has become many thousand times larger than the body of the worm whence it proceeded. It must be allowed that Schneider’s description and accompanying figures are very convincing. When revising the entozoa of the Hunterian Collection in 1866 I explained the specimens and dissections in accordance with Lubbock’s views. In the following year Prof. Huxley in his College Lectures supported the view of Schneider, but in his recently published manual the opinions of the Berlin helminthologist are not so much as alluded to.
Another point of special interest in connection with the parasites of insects concerns the development of Mermis albicans. At or near the time of the maturation of the ova, the parent worm, hitherto lodged within the body of some insect, buries itself in the soil. It commences its migration by boring its way out of the body of the host. Some difference of opinion exists as to the condition of the parent at the time of its wandering, for Von Siebold asserted that it quitted its parasitical mode of life “in order to become sexually mature away from the animal” infested; whereas Van Beneden states that the embryos are always formed at the time of the wandering.
From Von Siebold’s experiments it would appear that incompletely developed Mermes can become mature whilst still in the soil; but the normal condition requires the wandering to commence, as we have said, at or near the full time of embryonal development. The embryos are reproduced viviparously, and being set free, they pass a certain period of their existence in the soil. Here they grow rapidly, acquire sexual organs, and subsequently seek to “gratify their immigrative propensities,” as Von Siebold says, by selecting and penetrating the soft-bodied larvæ of lepidopterous and other insects. This entrance they accomplish by means of a sharply-pointed dentule or boring stylet, which at the time of disuse is concealed within the head. Having once gained access to the host they remain within its body until the caterpillar has become transformed into the perfect butterfly, or until their own sexual maturity is completed. Van Beneden thinks it probable that the males quit the host some time before the females, a view which, if correct, might alone account for the comparative scarcity of the males. According to Von Siebold, sexual congress occurs before the entrance of the worm into the caterpillar. This observation agrees with the generally admitted fact that hitherto no male Mermes have actually been detected in the bodies of insects. The Gordii, like Mermes, become free in damp earth and penetrate the bodies of certain insects or their larvæ. Some of them gain access to fishes. Like the free nematodes (Anguillulidæ), many of the Gordii will survive complete desiccation. The eggs of the mature worms are deposited in long agglutinated chains in water or damp situations.
I must conclude. In the body of this work will be found many notices of insect parasites that are awaiting transference to some vertebrate. I need only allude to the rôle of the mosquito, to that of the louse of the dog, and especially to that of the little myriapod (Glomeris) which, like the common glow-worm (Lampyris), possesses phosphorescent properties. I mention this again partly in correction of an entomological error (at p. [296]) which escaped me at the time of going to press. Leidy has described a mature nematode (Ascaris infecta) from Passalus cornutus, and numerous Filariæ are known to infest insects (Blatta, Forficula, Phosphuga, &c., &c.). From an earwig I obtained a filaria nearly five inches in length.
We have seen that the larvæ of Dracunculus, Cucullanus, as well as those of other important nematodes, dwell in bodies of entomostracous crustacea, whilst those of Echinorhynchus attack the Gammari and their allies. The well-known Udonella caligorum attaches itself to crustacea that are themselves parasitic.