20 On the Hirudo Australia. 



others recommend water alone, changing it every second or 

 third day. 



Leeches, although very tenacious of life, hecome sickly 

 soon, should the temperature be below 50 deg., or above 90 

 deg. Fah. Under 50 deg. they are liable to a disease which 

 appears in the shape of a ring round the body, gradually 

 tightening until it destroys life. Exposed to a high tempera- 

 ture, the water becomes speedily tainted and impure, as each 

 leech throws off a slimy coat every fifth day ; this alone is 

 sufficient to destroy life, as the decomposition of animal 

 matter is very rapid in a temperature so variable as ours. 



The object of the charcoal is undoubtedly to prevent the 

 rapidity of decomposition, as well as to assist them in extri- 

 cating themselves from their worn-out coats ; and the turf 

 moss is useful for the same purpose as well as for food. 



I am under the impression that their food consists not only 

 of animalculse and larvse, but also of the coloring matter of 

 the marls or clays. I have noticed that after remaining for 

 some time in the yellow or blue clay, they assume a strong 

 shade of either color. 



The plan I adopt for their preservation is simple, natural, 

 and every way successful. For their preservation and culti- 

 vation on a large scale, sink into the earth, in a place pro- 

 tected from the sun and weather, a given circle ; bank well 

 up the sides, and half fill with the finest red or blue marl or 

 clay, made into the consistence of thick mud (the red clay is 

 preferable), and in this place the leeches; cover it over with 

 thin canvas or calico, to exclude from them the extreme rays 

 of light, and occasionally sprinkle the top of the clay with 

 fresh rain water. The leeches will make no attempt to rise 

 above the surface of the clay, but suit themselves to the tem- 

 perature by rising or sinking accordingly. 



By this simple plan of keeping them, they are not only able 

 to clear themselves of their mucous coat, but can supply them- 

 selves with such food as improves their condition, and ren- 

 ders them more fit for the purpose required of them. 



The low lands of Germany, the lakes of Siberia, Bohemia, 

 and other parts of Europe, which have supplied the markets 

 for so long, are becoming rapidly exhausted. 



The demand for leeches on the Continent, and also Great 

 Britain, continues to be enormous. It has been computed 

 that 600,000 are monthly imported into London, over 

 7,000,000 annually ; and that 3,000,000 are annually con- 

 sumed in Paris. 



