The instinct of the crocodile to resort to the same expedient has been already referred to[1], and in like manner the fish, when distressed by the evaporation of the tanks, seek relief by immersing first their heads, and by degrees their whole bodies, in the mud; and sinking to a depth at which they find sufficient moisture to preserve life in a state of lethargy long after the bed of the tank has been consolidated by the intense heat of the sun.  It is possible, too, that the cracks which reticulate the surface may admit air to some extent to sustain their faint respiration.

[Footnote 1:  See ante, P. II. ch. iii. p. 189.]

The same thing takes place in other tropical regions, subject to vicissitudes of draught and moisture.  The Protopterus[1] which inhabits the Gambia (and which, though demonstrated by Professor Owen to possess all the essential organisation of fishes, is nevertheless provided with true lungs), is accustomed in the dry season, when the river retires into its channel, to bury itself to the depth of twelve or sixteen inches in the indurated mud of the banks, and to remain in a state of torpor till the rising of the stream after the rains enables it to resume its active habits.  At this period the natives of the Gambia, like those of Ceylon, resort to the river, and secure the fish in considerable numbers as they flounder in the still shallow water.  A parallel instance occurs in Abyssinia in relation to the fish of the Mareb, one of the sources of the Nile, the waters of which are partially absorbed in traversing the plains of Taka.  During the summer its bed is dry, and in the slime at the depth of more than six feet is found a species of fish without scales, different from any known to inhabit the Nile.[2]

[Footnote 1:  Lepidosiren annectans, Owen.  See Linn.  Trans. 1839.]

[Footnote 2:  This statement will be found in QUATREMERE’S Memoires sur l’Egypte, tom. i. p. 17, on the authority of Abdullah ben Ahmed ben Solaim Assouany, in his History of Nubia, “Simon, heritier presomptif du royanme d’Alouah, m’a assure que l’on trouve, dans la vase qui couvre le fond de cette riviere, un grand poisson sans ecailles, qui ne ressemble en rien aux poissons du Nil, et que, pour l’avoir, il faut creuser a une toise et plus de profondeur.”  To this passage there is appended this note:—­“Le patriarche Mendes, cite par Legrand (Relation Hist. d’Abyssinie, du P. LOBO, p. 212-3) rapporte que le fleuve Mareb, apres avoir arrose une etendue de pays considerable, se perd sous terre; et que quand les Portugais faisaient la guerre dans ce pays, ils fouilloient dans le sable, et y trouvoient de la bonne eau et du bon poison.  Au rapport de l’auteur de l’Ayin Akbery (tom. ii. p. 146, ed. 1800), dans le Soubah de Caschmir, pres du lieu nomme Tilahmoulah, est une grande piece de terre qui est inondee pendant la saison des pluies.  Lorsque les eaux se sont evaporees, et que la vase est presque