3414 



THE WORM-LIKE ANIMALS 



sucker. The structure of the organs that have been just described explains the 

 utility of the leech as a blood-letter. The creature adheres to the spot upon which 

 it is placed by means of its front sucker, which has the mouth in the middle of it. 

 The jaws are then brought to bear upon the skin and start sawing their way into 

 it, while the blood that flows from the wound passes into the sacs of the stomach 

 until they are all filled; and since the walls of the body as well as those of the alimen- 

 tary canal are highly elastic, it is easy to understand how the creature, is able to ex- 

 pand to two or three times its normal size. Some of the structural points enumer- 

 ated above are shown in the illustration on the next page, in which i is the 

 alimentary canal, with the oesophagus (#) and the sacs of the stomach (b and c}; 2 

 is the head end showing the eye spots; and 3 is part of one of the jaws. 



Leeches are found in marshes and ponds with a bottom of mud or clay, and 

 overgrown with weeds. They cannot live long out of water and die as soon as 



the skin dries, though for some 

 time they may protect them- 

 selves from this by the 

 excretion of slimy matter. 

 By day, and especially in 

 warm weather, they swim 

 about with liveliness, but at 

 night and in dark, foggy 

 weather, or on cold days they 

 remain quiet and curled up, 

 and in the autumn they 

 bury themselves deep in the 

 mud. They feed largely 

 upon the blood of fishes, 

 frogs, or mammals, but some- 

 times, in cases of necessity, 

 devour each other. After 

 pairing in the spring, the 

 suctional leeches bore into the 

 soft spongy ground just above 

 the level of the water, and at 



the end of July or thereabouts begin to form their cocoons or egg cases, one of 

 which is shown at D in the above illustration. These cocoons are formed of a 

 greenish mucus, or slimy material, and in them from ten to sixteen eggs are laid. 

 The mother then closes the aperture, and over the whole pours out a whitish saliva- 

 like froth, which upon drying forms a spongy coating to the case. The cocoons 

 are placed in the burrows, and from four to six weeks after the laying, the young 

 creep forth. These are thread-like and clear, but like the old ones in form; and 

 appear to attain their full size in about five years, although they may live as many as 

 twenty. 



The color of the medicinal leech is black above, generally ornamented with pale 

 bands. This species extends over the greater part of Europe, and has been found 



COMMON LEECH. 



A. From above (natural size) ; B. From the side, swimming (natural 

 size) ; C. Head cut open to show mouth (enlarged) ; D. Egg cocoon 

 (enlarged). 



