9g ZOOLOGY. 
much overrated. They have been made to fast two or three years; they 
require five years to become large enough for use, and they may live twenty 
years. They seem not to multiply rapidly when they have not access to 
blood; and on this account, cows and horses are driven into the breeding 
ponds, and so frequently, that they become emaciated from the loss of 
blood. Three millions of leeches are used annually in Paris; and four 
dealers in London import upwards of seven millions annually. In 1819, 
five or six millions were used in Paris, at a cost of 120,000 francs; and in 
1827, thirty-three millions were required in France. To preserve them in 
health, they must have clay, sticks, &., to crawl amongst, to assist them in 
casting the skin, this part being often renewed ; and if the old surface is not 
removed, respiration is interfered with. 
ened who insists upon the identity of the Annelida and Entozoa, hale 
the Panily which includes Sipunculus (p. 42) next to the inulin 
fam. 2. Lumbricide. The genus Lumbricus (pl. T7, figs. 38, 44) 
contains the earth-worms, known by their habits of living in the earth, and 
coming to the surface in wet weather and at night. The body is reddish 
or bluish, cylindrical, composed of many rings, the head indistinct, the 
mouth without teeth, and having neither eyes nor tentacles. The segments 
are provided beneath with minute bristles, and above with one or two 
pores. At certain periods, in some of the species, the part of the body con- 
taining the reproductive organs has a broad collar named the clitellum. 
These worms are monoicous, they feed upon the organic matter contained 
In the soil, generally ejecting the indigestible portion at the surface of, 
the ground. Some species live in the soft mud at the bottom of streams, 
and the ordinary species may be kept in vessels of mud and water. The 
largest European species is a foot and a half long, but there are several 
exotic species several feet in length. 
Earth-worms are very useful to the soil, as their perforations open it and 
allow the air and moisture to penetrate. They also assist in ameliorating 
it, and in increasing its depth; and where they are abundant, it is probable 
that every inch of soil has passed through their digestive system. In old 
unploughed pastures the soil formed by their castings is known to have 
amounted to an inch in depth in five years. 
Nais (pl. T7, figs. 9, 10), which belongs to this family, has the segments 
with lateral spines or fascicles. The old genus thus named by Miller, has 
been subdivided by more recent writers. They inhabit the fresh waters. 
Tubifex is a genus of microscopic worms found in fresh water, where 
they form a tube in the mud, whence they project the greater part of the 
body, waving it about, but instantly withdrawing when disturbed. Several 
species of the United States have been described. 
Fam. 3. Echiuwri. These have been alluded to in page 42. The body 
is short, composed of but few indistinct articulations, cylindrical, sacciform, 
provided with pairs of retractile bristles upon some of the segments. 
Thalassema echiurus, of the European seas, is the best known species. 
Fam. 4. Maldanie. This is one of the families of the distinguished 
naturalist Savigny, who accompanied the French expedition to Egypt. In 
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