546 THE POPULAR SCIENCE MONTHLY. 



The lakes to which we have devoted the greatest attention, and 

 which are at the same time the most common and the most interest- 

 ing, are those which fill glacier-worn rock-basins, to which we hope 

 that, our little article will attract the attention of some one who will 

 give us more light on these wonderful pictures, now but imperfectly 

 illuminated. 







AMPHIBIOUS FISHES. 1 



Bt e. sauvage. 



IN the swamps of the Gambia, after they have been dried by the 

 tropical sun, there are to be found here and there beneath the 

 surface clods of earth uniform in shape, and usually about the size of 

 a man's two fists. These clods inclose living animals, which have 

 been led by instinct to hide themselves away toward the close of the 

 rainy season, and before the coming of the season of drought, by 

 burying themselves in the mud while it was yet soft, and before it 

 had been hardened by the scorching rays of the sun. 



On breaking one of these lumps of mud, it is found to be a sort 

 of pouch or cocoon, with thin walls, and with projections here and 

 there corresponding to the form of the animal concealed within. Its 

 larger end is rounded, but its narrower end is closed by a slightly 

 convex lid with a narrow opening in the centre. If the surface of the 

 cocoon be even gently touched, a pretty loud cry is heard which Nat- 

 terer has compared to the mewing of a cat. 



For a long time it was supposed that the animal buried itself 

 amid the leaves which surround its protecting sheath. In a special 

 memoir published in the Bulletins of the St. Petersburg Academy of 

 Sciences, Leuckart expressed the opinion that the epidermis, by be- 

 coming detached, supplied the materials for this envelope. But since 

 his time it has been demonstrated that the cocoon is formed from a 

 dense secretion of mucus ; such is the result of observations made by 

 Paulson and Richard Owen, and repeated by Auguste Dumeril, Pro- 

 fessor of Ichthyology at the Museum. He has himself witnessed the 

 formation of the cocoon, and his description of the process we repeat 

 here in his own words. He says : 



" Two protopteri, that had been restored to freedom by the gradual soften- 

 ing of the clods in which they had been inclosed, evinced signs, after living for 

 a month in an aquarium, that the time had come for them to seek, in the soft 

 earth covered by the water, the shelter which they require during the dry season. 

 Their restlessness, their abundant secretion of mucus, their attempts at burrow- 

 ing, all showed an irresistible desire to find a medium different from that in 

 which they then lived. 



1 Translated from the French, by J. Fitzgerald, A. K 



