[Footnote 2: For a similar fact relative to the sh.e.l.ls and water beetles in the pools near Rio Janeiro, see DARWIN'S _Nat. Journal_, ch. v. p.

90. BENSON, in the first vol. of _Gleanings of Science_, published at Calcutta in 1829, describes a species of _Paludina_ found in pools, which are periodically dried up in the hot season but reappear with the rains, p. 363. And in the _Journal of the Asiatic Soc. of Bengal_ for Sept. 1832, Lieut. HUTTON, in a singularly interesting paper, has followed up the same subject by a narrative of his own observations at Mirzapore, where in June, 1832, after a few heavy showers of rain, which formed pools on the surface of the ground near a mango grove, he saw the _Paludinae_ issuing from the ground, "pushing aside the moistened earth and coming forth from their retreats; but on the disappearance of the water not one of them was to be seen above ground. Wishing to ascertain what had become of them, he turned up the earth at the base of several trees, and invariably found the sh.e.l.ls buried from an inch to two inches below the surface." Lieut. Hutton adds that the _Ampullariae_ and _Planorbes_, as well as the _Paludinae_, are found in similar situations during the heats of the dry season. The British _Pisidea_ exhibit the same faculty (see a monograph in the _Camb. Phil. Trans._ vol. iv.). The fact is elsewhere alluded to in the present work of the power possessed by the land leech of Ceylon of retaining vitality even after being parched to hardness during the heat of the rainless season. Vol. I. ch.

vii. p. 312.]

Dr. John Hunter[1] has advanced the opinion that hybernation, although a result of cold, is not its immediate consequence, but is attributable to that deprivation of food and other essentials which extreme cold occasions, and against the recurrence of which nature makes a timely provision by a suspension of her functions. Excessive heat in the tropics produces an effect upon animals and vegetables a.n.a.logous to that of excessive cold in northern regions, and hence it is reasonable to suppose that the torpor induced by the one may be but the counterpart of the hybernation which results from the other. The frost which imprisons the alligator in the Mississippi as effectually cuts him off from food and action as the drought which incarcerates the crocodile in the sun-burnt clay of a Ceylon tank. The hedgehog of Europe enters on a period of absolute torpidity as soon as the inclemency of winter deprives it of its ordinary supply of slugs and insects; and the _Tenrec_[2] of Madagascar, its tropical representative, exhibits the same tendency during the period when excessive heat produces in that climate a like result.

[Footnote 1: HUNTER'S _Observations on parts of the Animal Oeconomy_, p.

88.]

[Footnote 2: _Centetes ecaudatus_, Illiger.]

The descent of the _Ampullaria_, and other fresh-water molluscs, into the mud of the tank, has its parallel in the conduct of the _Bulimi_ and _Helices_ on land. The European snail, in the beginning of winter, either buries itself in the earth or withdraws to some crevice or overarching stone to await the returning vegetation of spring. So, in the season of intense heat, the _Helix Waltoni_ of Ceylon, and others of the same family, before retiring under cover, close the aperture of their sh.e.l.ls with an impervious epiphragm, which effectually protects their moisture and juices from evaporation during the period of their aestivation. The Bulimi of Chili have been found alive in England in a box packed in cotton after an interval of two years, and the animal inhabiting a land-sh.e.l.l from Suez, which was attached to a tablet and deposited in the British Museum in 1846, was found in 1850 to have formed a fresh epiphragm, and on being immersed in tepid water, it emerged from its sh.e.l.l. It became torpid again on the 15th November, 1851, and was found dead and dried up in March, 1852.[1] But the exceptions serve to prove the accuracy of Hunter's opinion almost as strikingly as accordances, since the same genera of animals which hybernate in Europe, where extreme cold disarranges their oeconomy, evince no symptoms of lethargy in the tropics, provided their food be not diminished by the heat. Ants, which are torpid in Europe during winter, work all the year round in India, where sustenance is uniform.[2] The Shrews of Ceylon (_Sorex monta.n.u.s_ and _S. ferrugineus_ of Kelaart) which, like those at home, subsist upon insects, inhabit a region where the equable temperature admits of the pursuit of their prey at all seasons of the year; and hence, unlike those of Europe, they never hybernate. A similar observation applies to the bats, which are dormant during a northern winter when insects are rare, but never become torpid in any part of the tropics.

[Footnote 1: _Annals of Natural History_, 1850. See Dr. BAIRD's _Account of Helix desertorum; Excelsior, &c._, ch. i. p. 345.]

[Footnote 2: Colonel SYKES has described in the _Entomological Trans._ the operations of an ant which laid up a store of hay against the rainy season.]

The bear, in like manner, is nowhere deprived of its activity except when the rigour of severe frost cuts off its access to its accustomed food. On the other hand, the tortoise, which immerses itself in indurated mud during the hot months in Venezuela, shows no tendency to torpor in Ceylon, where its food is permanent; and yet is subject to hybernation when carried to the colder regions of Europe.

To the fish in the detached tanks and pools when the heat, by exhausting the water, deprives them at once of motion and sustenance, the practical effect must be the same as when the frost of a northern winter encases them in ice. Nor is it difficult to believe that they can successfully undergo the one crisis when we know beyond question that they may survive the other.[1]

[Footnote 1: YARRELL, vol. i. p. 364, quotes the authority of Dr. J.

Hunter in his _Animal OEconomy_, that fish, "after being frozen still retain so much of life as when thawed to resume their vital actions;"

and in the same volume (_Introd._ vol. i. p. xvii.) he relates from JESSE'S _Gleanings in Natural History_, the story of a gold fish (_Cyprinus auratus_) which, together with the water in a marble basin, was frozen into one solid lump of ice, yet, on the water being thawed, the fish became as lively as usual Dr. RICHARDSON, in the third vol. of his _Fauna Borealis Americana_, says the grey sucking carp found in the fur countries of North America, may be frozen and thawed again without being killed in the process.]

_Hot-water Fishes_.--Another incident is striking in connection with the fresh-water fishes of Ceylon. I have mentioned elsewhere the hot springs of Kannea, in the vicinity of Trincomalie, the water in which flows at a temperature varying at different seasons from 85 to 115. In the stream formed by these wells M. Reynaud found and forwarded to Cuvier two fishes which he took from the water at a time when his thermometer indicated a temperature of 37 Reaumur, equal to 115 of Fahrenheit. The one was an Apogon, the other an Amba.s.sis, and to each, from the heat of its habitat, he a.s.signed the specific name of "Thermalis."[1]

[Footnote 1: CUV. and VAL., vol. iii. p. 363. In addition to the two fishes above named, a loche _Cobitis thermalis_, and a carp, _Nuria thermoicos_, were found in the hot-springs of Kannea at a heat 40 Cent., 114 Fahr., and a roach, _Leuciscus thermalis_, when the thermometer indicated 50 Cent., 122 Fahr.--_Ib_. xviii. p. 59, xvi. p.

182, xvii. p. 94. Fish have been taken from a hot spring at Pooree when the thermometer stood at 112 Fahr., and as they belonged to a carnivorous genus, they must have found prey living in the same high temperature.--_Journ. Asiatic Soc. Beng_. vol. vi. p. 465. Fishes have been observed in a hot spring at Manilla which raises the thermometer to 187, and in another in Barbary, the usual temperature of which is 172; and Humboidt and Bonpland, when travelling in South America, saw fishes thrown up alive from a volcano, in water that raised the temperature to 210, being two degrees below the boiling point. PATTERSON'S _Zoology_.

Pt. ii p. 211; YARRELL'S _History of British Fishes_, vol. i. In. p.

xvi.]

_List of Ceylon Fishes._

I. OSSEOUS.

Acanthopterygii.

_Perca_ argentea, _Bennett_.

Apogon roseipinnis, _Cuv. & Val_.

Zeylonicus, _Cuv. & Val_.

thermalis, _Cuv. & Val_.

Amba.s.sis thermalis, _Cuv. & Val_.

Serra.n.u.s biguttatus, _Cuv. & Val_.

Tankervillae, _Benn_.

lemniscatus, _Cuv. & Val_.

Sonneratii, _Cuv. & Val_.

flavo-ceruleus, _Lacep_.

marginalis, _Cuv. & Val_.

Boelang, _Cuv. & Val_.

Serra.n.u.s faveatus, _Cuv. & Val_.

angularis, _Cuv. & Val_.

punctulatas, _Cuv. & Val_.

Diacope decem-lineatus, _Cuv. & Val_.

spilura, _Benn_.

xanthopus, _Cuv. & Val_.

Mesoprion annularis, _Cuv. & Val_.

Holocentrus orientale, _Cuv. & Val_.

spinifera, _Cuv. & Val_.

argenteus, _Cuv. & Val_.

Upeneus taeniopterus, _Cuv. & Val_.

Zeylonicus, _Cuv. & Val_.

Russeli, _Cuv. & Val_.

cinnabarinus, _Cuv. & Val_.

Platycephalus punctatus, _Cuv. & Val_.

scaber, _Linn_.

tuberculatus, _Cuv. & Val_.

serratus, _Cuv. & Val_.

Pterois volitans, _Gm_.

muricata, _Cuv. & Val_.

Diagramma cinerascens, _Cuv. & Val_.

Blochii, _Cuv. & Val_.

poeciloptera, _Cuv. & Val_.

Cuvieri, _Benn_.

Sibbaldi, _E. Benn_.

Lobotes crate, _Cuv. & Val_.

Scolopsides bimaculatus, _Rupp_.

Amphiprion Clarkii, _J. Benn_.

Dascyllus arua.n.u.s, _Cuv. & Val_.

Glyphisodon Rahti, _Cuv. & Val_.

Brownrigii, _Benn_.

_Sparus_ Hardwickii, _J. Benn_.

Pagrus longifilis, _Cuv. & Val_.

Lethrinus opercularis, _Cuv. & Val_.

fasciatus, _Cuv. & Val_.

fraenatus, _Cuv. & Val_.

cythrurus, _Cuv. & Val_.

cinereus, _Cuv. & Val_.

Smaris balteatus, _Cuv. & Val_.

Caesio coerulaureus, _Lacep_.

Gerres oblongus, _Cuv. & Val_.

Chaetodon vagabundus, _Linn_.

Seba.n.u.s, _Cuv. & Val_.

Layardi, _Blyth_.

xanthocephalus, _E. Bennett_.

guttatissimus, _E. Benn_.

Haeniochus macrolepidotus, _Linn_.

Scatophagus argus, _Cuv. & Val_.

Holacanthus xanthurus, _E. Benn_.