Part II (Reptilia).

Much that I have advanced in respect of the parasitism of birds holds good in the case of reptiles. I cannot recapitulate. The saurians, ophidians, and chelonians are extensively infested, but in this respect the amphibian frogs, toads, and salamanders are probably the most victimised. If, on the one hand, comparatively few tapeworms have been found in reptiles, it may, on the other hand, be said that the Echinorhynchi come into prominence, causing serious injury to reptilian hosts. Serpents and chameleons are particularly liable to have their lungs infested by acanthocephalous entozoa, these organs being also attacked by pentastomes. I have received evidence of fatal epizoöty amongst chameleons from this source; and I have been requested to suggest a remedy. To prevent outbreaks of entozoal disease is one thing; to offer a radical cure when the parasites are firmly anchored within the pulmonary organs is quite another matter.

As remarked in my ‘Entozoa,’ the trematodes display a great partiality for batrachians, more than half a dozen different species of fluke being known to infest the common frog. Flukes are likewise tolerably abundant in the saurian and chelonian reptiles. I regret that I cannot find space so much as to enumerate the species. As one would naturally expect, the frog has been exhaustively anatomised and examined for entozoa, and it was this creature that supplied Leuckart and Mecznikow with the materials which led to their well-known discovery and controversy respecting the development, dimorphism, and parthenogenetic phenomena exhibited by Ascaris nigrovenosa. I cannot give the facts in detail. Female examples of the worm live in the lungs of the frog. Their young, as embryos, pass into the damp earth and mud, where they grow up into sexually-mature forms different from the parent worms found in the frog. These free adult worms, male and female, produce rhabditiform embryos which present characters of their own and attain a certain stage of growth. At this stage they are conveyed into the lungs of the frog where they arrive at sexual maturity. As there are no male worms in the frog, it is probable that the embryos of these parasitic females are agamogenetically produced by internal budding, the sexual influence of the free males being, as it were, continued onward without actual contact with the parasitic females. Amongst the interesting parasites of the frog one must also mention Amphistoma subclavatum and Polystoma intergerrimum. The former worm resides in the large intestine and the latter in the urinary bladder. The larvæ (Cercaria diplocotylea) of this amphistome reside in or upon the body of water-snails, and, like the cercarian larvæ of polystoma, they are furnished with eyes. I state this fact on the authority of Pagenstecher; and, since I cannot devote a special section to the entozoa of mollusks, I repeat, in part, the valuable results which Pagenstecher published many years back and which have a permanent value in relation to the origin of parasitic diseases resulting from flukes. In the memoir quoted below, Pagenstecher gives the following conclusions (Schlussbemerkungen):

“(a).—The eggs of the trematoda vary in respect of size, form, and color, being either furnished or not with a lid, and accordingly distinguishable. In the mature condition they contain a ciliated or a non-ciliated embryo of unequal growth, this embryo partly increasing in size even after its birth. In various conceivable ways the eggs themselves, or the embryos which have quitted their shells, arrive in and upon the bodies of mollusks, where they are consequently found. In this situation the egg opens, or the ciliated covering decays, and the contained motionless germ—which in itself offers no distinctive characters—having become free, grows into a nurse, or forms several nurses within itself.

“(b).—Whilst some of the trematodes display a highly organised nurse condition, others exhibit only a simple kind of germ-sac. Both forms, nevertheless, appear to occur in one and the same species, probably depending upon external causes.

“(c).—The organised nurses (or rediæ, as they are termed) have a mouth and a strongly marked muscular œsophagus, which is continued into a short or prolonged, single, blind intestine, or the latter may be double. The expulsion of animals developed within them I have only seen to take place through an opening at the hinder extremity. Old rediæ lose their structure. I did not observe any vascular system. Tailed trematode larvæ (Cercariæ), as well as rediæ themselves, are developed within the rediæ, this variation of nurse-contents probably depending on the season.

“(d).—No independent new germ-sacs are developed within the simple unorganised germ-sacs (sporocysts), and only such trematode larvæ as are capable of arriving at sexual maturity are furnished with special appendages.

“(e).—When the immature contents of both nurse forms (i.e. of sporocysts and rediæ) are accidentally set free, and are situated within the organs of nutrition of the living host, then they appear prepared to develop themselves anew into nurse forms; and, moreover, cercariæ whose development has not yet attained a definite stage—and even their tails also—appear to enjoy a similar capacity. Some nurses are likewise capable of multiplication by division and budding.

“(f).—Some germ-sacs have the property of developing within themselves cercaria-like larvæ—which are different from the true cercariæ—from whose body the development of a distoma may take place, while their single or double tail-like appendages in all cases develop anew into germ-sacs. To this class belong Bucephalus and Distoma duplicatum.

“(g).—All the cercaria at present known are destitute of eyes, but other forms of trematode larvæ are furnished with visual organs. Accordingly, I never found eyes in young distomata whilst they were in their last dwelling-place, but eyes are certainly present in the young forms of Polystoma and Amphistoma. The supposition that a spontaneous wandering is associated with eyes is not yet confirmed in my experience.

“(h).—As a means of distinguishing the different forms of Cercariæ, amongst other indications, their places of dwelling may be useful, because each mollusk only harbors a limited number of species. Notwithstanding, Professor Filippi is in error if he believes that every species of mollusk carries only a single armed form of cercaria. A migration of the cercaria is indispensable to its perfection.

“(i).—Many larval trematodes form cysts round themselves, probably by means of a special organ of secretion, and also by the epidermis. Their future destiny necessitates this. The sporocysts apparently fulfil towards the larvæ, which are developed within them, a similar purpose, namely, a protection against the stomachal digestion of the new host. In the pupa condition the development of the larva, which has now thrown off the tail, makes greater or less progress, according as to whether it is surrounded by nourishment or not. In particular, while in this stage, the different kinds of hooks for migratory purposes make their appearance, always, without doubt, after the shedding of the skin. Other trematodes pass through this tail-less sexually-immature stage without any cyst. I have not yet seen any larval trematode forms which had been produced in sporocysts or rediæ without appendages; they appear to occur, nevertheless.

“(k).—As the larvæ exist only in a few hosts—and most of them dwell only in one species of animal—so, also, the continued progress towards sexual maturity only succeeds in the case of certain well-defined larval organisms, but the digestion of the cysts and liberation of the larvæ may be accomplished in various animals.

“(l).—The armed Cercariæ appear to be larvæ of the spine-covered distomes of amphibia; for, as examples, the Cercaria ornata becomes transformed into Distoma clavigerum, and C. armata into Distoma endolobum; the Dist. duplicatum and Cerc. diplocotylea are, apparently, the juvenile forms of Dist. cygnoides and Amphistoma subclavatum. The Dist. echiniferum of Paludina could neither be advanced in development in the frog or duck, nor could all the other larvæ which I subjected to experiment be developed either in the green or brown frogs.

“(m).—When young trematodes arrive at the right place for their maturation, then the male generative structures develop before the female organs, and in the subsequent excess of egg production the form and structure of the animal becomes obliterated.

“(n).—The yelk-molecules surrounding the germinal vesicle are not directly transformed into an embryo.”

Fig. 76.—Echinorhynchus anthuris. 1, Attached to the intestine; 2, speci­men en­larged; 3, ovarian vesicle, including germs; 4, germs in various stages; 5, vesicle with germs more advanced; 6, 7, eggs in their capsules; 8, free egg. Original.

As regards the acantho­cephalous parasites of reptiles, I may observe that Echino­rhynchus anthuris is very common in the lesser water newt (Lisso­triton punc­tatus). In the accompanying illustration (Fig. 76) I have represented the free ovarian egg-bearing bodies, the development of the ovum, and the adult worms. For anatomical details, however, I must refer to my earlier treatise (‘Entozoa,’ p. 100 et seq.).

Amongst the species of entozoa that were found by me at the Zoological Society’s Menagerie I may mention Distoma coronarium and Ascaris lineata, from the intestines of Alligator mississippiensis; Dist. Boscii, from an American snake (Coluber); an immature nematode, from the heart of Coluber Blumenbachii; and Echinorhynchus inflexus, attached to the intestines of a snapping turtle (Chelydra serpentina). I may add that the lungs of the alligator also contained examples of Diesing’s Pentastoma oxycephalum. An Egyptian hooded snake (Naia haje), which died at the Zoological Gardens in 1859, furnished a new species of pentastome (P. multicinctum). Dr George Harley described and anatomised this worm with remarkable care. To Harley’s memoir Prof. Leuckart did ample justice in his work on the ‘Pentastoma.’ Several new species of reptilian entozoa have recently been described by Dr von Linstow; and Dr Solger has found a new trichosome (T. recurvum) beneath the skin of a young crocodile (probably Croc. acutus). For further particulars I refer to the revised descriptions and additions by Diesing, Molin, Schneider, and other systematists.

Bibliography (No. 58).—Baird, W., “Description of a new Entozoon from the Diamond Snake,” in ‘Proceed. Zool. Soc.’ for 1865, p. 58, and in ‘Ann. Nat. Hist.’ for July, 1865, p. 52.—Blanchard, “On Polystoma,” ‘Ann. des Sci. Nat.,’ 3e ser., viii, p. 331.—Canton, E., “An account of some Parasites attached to the Conjunctivæ of the Turtle’s Eyes,” ‘Quart. Journ. Micr. Sci.,’ and ‘Dublin Med. Press,’ 1861 (with remarks by myself).—Cobbold, ‘Notes,’ &c. (l. c., Bibl. No. [57]), and in ‘Linn. Trans.,’ 1857.—Crisp, E., “Note on Cysticerci and Trichocephali from an Alligator,” ‘Path. Soc. Trans.,’ 1854.—Diesing, ‘Revision der Cercarieen,’ 1858; ‘Revis. der Myzelminthen,’ 1858; ‘Nachträge (u. s. w.),’ 1859; ‘Revis. der Nematoden,’ 1860; ‘Revis. d. Turbellarien,’ 1861; ‘Revis. d. Cephalocotyleen,’ 1863.—Idem, ‘Monographie d. Gatt. Amphistoma und Diplodiscus,’ and ‘Nachträge zur Monog. der Amph.,’ 1839.—Dujardin, ‘Hist. d. Helm.’ (l. c., pp. 320, 526, &c.).—Eberth, “On Myoryktes Weismanni from the Muscles of the Frog,” trans. by Busk, from ‘Siebold und Kölliker’s Zeitschrift,’ in ‘Lond. Micr. Journ.,’ Jan., 1864.—Gastaldi, ‘Cenni sopra alcuni nuovi Elmint.,’ Torino, 1854 (new flukes from frogs and salamanders).—Glüge, “On Entozoa in the Vessels of Frogs,” from ‘Comptes Rendus,’ in ‘Micr. Journ. and Struct. Rec.,’ p. 207, 1842; see Grübe and Valentin.—Grübe, “On the Entozoa of the Frog, and on the Pathology of that Batrachian,” from ‘Comptes Rendus,’ in ‘Micr. Journ. and Struct. Rec.,’ p. 246, for 1842; see also Mandl.—Harley, G., “On the Anatomy of a new Species of Pentastoma found in the Lung and Air-sac of an Egyptian Cobra,” ‘Proc. Zool. Soc.,’ June, part xxv, p. 115, 1857.—Leuckart, ‘Bau und Entwickelungsgeschichte der Pentastomen,’ Leipsig, 1860.—Linstow, ‘Enthelminth.’ (l. c., Bibl. No. [57]).—Macalister, A., “On the presence of certain Secreting Organs in Nematoidea,” ‘Ann. and Mag. of Nat. Hist.’ for 1865.—Idem, “On the Anatomy of Ascaris dactyluris,” ‘Proc. Nat. Hist. Soc. of Dublin,’ vol. iv, 1865.—Mandl, “Development of Entozoa (Ascaris nigrovenosa of the frog),” from ‘Rep. of French Acad. of Sci.,’ in ‘Month. Journ. of Med. Sci.,’ vol. ii, p. 1081, 1842.—Molin, ‘Monog. del gen. Myzelminth; Mon. del gen. Physaloptera; Mon. del gen. Histiocephalus; Mon. del gen. Spiroptera;’ Wien, 1859–60.—Pagenstecher, ‘Trematodenlarven und Trematoden,’ Heidelberg, 1857.—Sibbald, J., “On the Nematoideum natricis,” ‘Path. Soc. Trans.,’ vol. viii, 1857.—Solger, “Ueber eine neue species von Trichosoma,” ‘Arch. f. Naturg.,’ 1877.—Valentin, “On Parasites in the Bladder of the Frog” (from ‘Repertorium’), in ‘Micr. Journ. and Struct. Record,’ 1842, p. 183.—Vogt, C., “On Filaria in the Vessels of the Frog,” from ‘Müller’s Archiv,’ in ‘Micr. Journ. and Struct. Rec.,’ p. 241, 1842.—Wedl, F., “Beiträge zur Lehre von den Hæmatozoen,” ‘Sitzungsb. Akad.,’ Wien, 1850 (from the blood of frogs, &c.).—Zeller, E., “Weiterer Beitrag zur Kentniss der Polystomen,” ‘Sieb. und Köll. Zeitschrift,’ 1875.