MALACOPTKRYGII APODES. 541 



the death of the fishes which are taken out of the water is the 

 desiccation which their gills undergo. But the eel can, 

 more easily than many others, close exactly the aperture of 

 this part and that of the mouth. Accordingly, it has been 

 observed that it can remain six or eight days out of the water, 

 when it is in a humid place, and the weather is not too warm ; 

 but if it be exposed to the sun, a very few moments are suffi- 

 cient to cause it to perish. This has been remarked as long 

 ago as the time of Pliny. 



During the day the eels remain almost always sunk in the 

 mud, or in holes which they have excavated in the banks, 

 sometimes very large, and inclosing a great number of them, 

 having almost always two apertures, by which they may 

 enter or go out indifferently in the moment of danger, for they 

 swim backwards almost as well as in the natural direction. 



AVhen the weather is very warm, and the water of the ponds 

 begins to be corrupted, the eels quit the bottom, and come to 

 the surface to respire a purer air. They then conceal them- 

 selves under the floating plants, or among those which border 

 the shore. 



This alteration of the waters is, in warm countries, one of 

 the most frequent causes of the mortality of the eels. Spal- 

 lanzani, who has made very extensive researches into their 

 manners, relates, that sometimes hundreds of thousands of 

 them perish in the ponds of Comachio, near Venice, ponds 

 which produce very considerable sums solely by being let out 

 for the fishery of these animals. 



In the northern parts of Europe, where putrid fermentation 

 proceeds more slowly, the eels are less exposed to accidents 

 of this nature ; nevertheless they sometimes contract a malady 

 which is indicated on their skin by a great number of white spots. 

 Eels have been known to live sometimes for months, nay, 

 for years, in the mud of dried up ponds, or in the holes of 

 rivers the course of which had been turned, deprived of water, 



